Kconfig: Add u-boot.itb BUILD_TARGET for Rockchip

Add u-boot.itb BUILD_TARGET for Rockchip platform when SPL_LOAD_FIT
is being used.

This can get rid of building itb explicitly with 'make u-boot.itb'
so, from now all required images will build just by make.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>

Kconfig

@@ -250,7 +250,7 @@ config BUILD_TARGET
 	default "u-boot-with-spl.sfp" if TARGET_SOCFPGA_GEN5
 	default "u-boot-spl.kwb" if ARCH_MVEBU && SPL
 	default "u-boot-elf.srec" if RCAR_GEN3
-	default "u-boot.itb" if SPL_LOAD_FIT && ARCH_SUNXI
+	default "u-boot.itb" if SPL_LOAD_FIT && (ROCKCHIP_RK3399 || ARCH_SUNXI)
 	default "u-boot.kwb" if KIRKWOOD
 	default "u-boot-with-spl.bin" if ARCH_AT91 && SPL_NAND_SUPPORT
 	help

board/theobroma-systems/puma_rk3399/README

@@ -60,7 +60,7 @@ Creating a SPL image for SD-Card/eMMC
 Creating a SPL image for SPI-NOR
   > tools/mkimage -n rk3399 -T rkspi -d spl/u-boot-spl.bin spl_nor.img
 Create the FIT image containing U-Boot proper, ATF, M0 Firmware, devicetree
-  > make CROSS_COMPILE=aarch64-linux-gnu- u-boot.itb
+  > make CROSS_COMPILE=aarch64-linux-gnu-
 
 Flash the image
 ===============

board/vamrs/rock960_rk3399/README

@@ -61,7 +61,6 @@ Compile the U-Boot
   > export CROSS_COMPILE=aarch64-linux-gnu-
   > make rock960-rk3399_defconfig
   > make
-  > make u-boot.itb
 
 Compile the rkdeveloptool
 =========================

doc/README.rockchip

@@ -104,7 +104,6 @@ For example:
      => cd /path/to/u-boot
      => make nanopi-neo4-rk3399_defconfig
      => make
-     => make u-boot.itb
 
    - Get the rkbin
 
@@ -171,7 +170,6 @@ For example:
      => cd /path/to/u-boot
      => make orangepi-rk3399_defconfig
      => make
-     => make u-boot.itb
 
      (Get spl/u-boot-spl-dtb.bin, u-boot.itb images and some boards would get
       spl/u-boot-spl.bin since it doesn't enable CONFIG_SPL_OF_CONTROL