spl: Create proper symbols for enabling the malloc() pool

For U-Boot proper we have CONFIG_SYS_MALLOC_F which indicates that a
malloc() pool is available before relocation.

For SPL we only have CONFIG_SPL_SYS_MALLOC_F_LEN which indicates the
size of the pool.

In various places we use CONFIG_SPL_SYS_MALLOC_F_LEN == 0 to indicate
that there is no pool.

This differing approach is confusing. Add a new CONFIG_SPL_SYS_MALLOC_F
symbol for SPL (and similarly for TPL and VPL). Tidy up the Kconfig
help for clarity.

For now these symbols are not used. That is cleaned up in the following
patches.

Signed-off-by: Simon Glass <sjg@chromium.org>

Kconfig

@@ -295,6 +295,16 @@ config SYS_MALLOC_LEN
 	  This defines memory to be allocated for Dynamic allocation
 	  TODO: Use for other architectures
 
+config SPL_SYS_MALLOC_F
+	bool "Enable malloc() pool in SPL"
+	depends on SPL_FRAMEWORK && SYS_MALLOC_F && SPL
+	default y
+	help
+	  In SPL memory is very limited on many platforms. Still,
+	  we can provide a small malloc() pool if needed. Driver model in
+	  particular needs this to operate, so that it can allocate the
+	  initial serial device and any others that are needed.
+
 config SPL_SYS_MALLOC_F_LEN
 	hex "Size of malloc() pool in SPL"
 	depends on SYS_MALLOC_F && SPL
@@ -303,23 +313,31 @@ config SPL_SYS_MALLOC_F_LEN
 	default 0x2000 if IMX8MQ
 	default SYS_MALLOC_F_LEN
 	help
-	  In SPL memory is very limited on many platforms. Still,
+	  Sets the size of the malloc() pool in SPL. This is used for
-	  we can provide a small malloc() pool if needed. Driver model in
+	  driver model and other features, which must allocate memory for
-	  particular needs this to operate, so that it can allocate the
+	  data structures.
-	  initial serial device and any others that are needed.
 
 	  It is possible to enable CFG_SPL_SYS_MALLOC_START to start a new
 	  malloc() region in SDRAM once it is inited.
 
+config TPL_SYS_MALLOC_F
+	bool "Enable malloc() pool in SPL"
+	depends on SYS_MALLOC_F && TPL
+	default y if SPL_SYS_MALLOC_F
+	help
+	  In TPL memory is very limited on many platforms. Still,
+	  we can provide a small malloc() pool if needed. Driver model in
+	  particular needs this to operate, so that it can allocate the
+	  initial serial device and any others that are needed.
+
 config TPL_SYS_MALLOC_F_LEN
 	hex "Size of malloc() pool in TPL"
 	depends on SYS_MALLOC_F && TPL
 	default SPL_SYS_MALLOC_F_LEN
 	help
-	  In TPL memory is very limited on many platforms. Still,
+	  Sets the size of the malloc() pool in TPL. This is used for
-	  we can provide a small malloc() pool if needed. Driver model in
+	  driver model and other features, which must allocate memory for
-	  particular needs this to operate, so that it can allocate the
+	  data structures.
-	  initial serial device and any others that are needed.
 
 config VALGRIND
 	bool "Inform valgrind about memory allocations"
@@ -336,15 +354,24 @@ config VALGRIND
 	  it can be handled accurately by Valgrind. If you aren't planning on
 	  using valgrind to debug U-Boot, say 'n'.
 
+config VPL_SYS_MALLOC_F
+	bool "Enable malloc() pool in VPL"
+	depends on SYS_MALLOC_F && VPL
+	default y if SPL_SYS_MALLOC_F
+	help
+	  In VPL memory is very limited on many platforms. Still,
+	  we can provide a small malloc() pool if needed. Driver model in
+	  particular needs this to operate, so that it can allocate the
+	  initial serial device and any others that are needed.
+
 config VPL_SYS_MALLOC_F_LEN
 	hex "Size of malloc() pool in VPL before relocation"
 	depends on SYS_MALLOC_F && VPL
 	default SYS_MALLOC_F_LEN
 	help
-	  Before relocation, memory is very limited on many platforms. Still,
+	  Sets the size of the malloc() pool in VPL. This is used for
-	  we can provide a small malloc() pool if needed. Driver model in
+	  driver model and other features, which must allocate memory for
-	  particular needs this to operate, so that it can allocate the
+	  data structures.
-	  initial serial device and any others that are needed.
 
 menuconfig EXPERT
 	bool "Configure standard U-Boot features (expert users)"