tools: mkimage: Extend mkimage to also include pmufw

The patch is adding external pmufw "Platform Management Unit firmware"
to boot.bin image. Boot.bin is a Xilinx format which bootrom is capable
to read and boot the system. pmufw is copied to the header data section
follows by u-boot-spl.bin. pmufw is consumed by PMU unit (Microblaze)
and SPL runs on a53-0.

This is generated command line when PMUFW_INIT_FILE is setup.

./tools/mkimage -T zynqmpimage -R ./"" -n
./"board/xilinx/zynqmp/pmufw.bin" -d spl/u-boot-spl.bin spl/boot.bin

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/cpu/armv8/zynqmp/Kconfig b/arch/arm/cpu/armv8/zynqmp/Kconfig
index 4dc8b1c..7a41583 100644
--- a/arch/arm/cpu/armv8/zynqmp/Kconfig
+++ b/arch/arm/cpu/armv8/zynqmp/Kconfig
@@ -57,6 +57,14 @@
 	  Add register writes to boot.bin format (max 256 pairs).
 	  Expect a table of register-value pairs, e.g. "0x12345678 0x4321"
 
+config PMUFW_INIT_FILE
+	string "PMU firmware"
+	depends on SPL
+	default ""
+	help
+	  Include external PMUFW (Platform Management Unit FirmWare) to
+	  a Xilinx bootable image (boot.bin).
+
 config ZYNQMP_USB
 	bool "Configure ZynqMP USB"