x86: Enable EFI loader support

Enable this so that EFI applications (notably grub) can be run under U-Boot
on x86 platforms.

At present the 'hello world' EFI application is not supported for the
qemu-x86_efi_payload64 board. That board builds a payload consisting of a
64-bit header and a 32-bit U-Boot, which is incompatible with the way the
EFI loader builds its EFI application. The following error is obtained:

x86_64-linux-ld.bfd: i386 architecture of input file
   `lib/efi_loader/helloworld.o' is incompatible with i386:x86-64 output

This could be corrected with additional Makefile rules. For now, this
feature is disabled for that board.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
[agraf: drop hello kconfig bits]
Signed-off-by: Alexander Graf <agraf@suse.de>

configs/efi-x86_defconfig

@@ -34,3 +34,4 @@ CONFIG_USB=y
 CONFIG_USB_STORAGE=y
 CONFIG_USB_KEYBOARD=y
 CONFIG_EFI=y
+# CONFIG_EFI_LOADER is not set

doc/README.x86

@@ -1077,7 +1077,6 @@ TODO List
 ---------
 - Audio
 - Chrome OS verified boot
-- Support for CONFIG_EFI_LOADER
 - Building U-Boot to run in 64-bit mode
 
 References

lib/efi_loader/Kconfig

@@ -1,6 +1,6 @@
 config EFI_LOADER
 	bool "Support running EFI Applications in U-Boot"
-	depends on ARM && OF_LIBFDT
+	depends on (ARM || X86) && OF_LIBFDT
 	default y
 	help
 	  Select this option if you want to run EFI applications (like grub2)