ARMv8: add optional Linux kernel image header

Allow placing a Linux kernel image header at the start of the U-Boot
binary. This is useful since the image header reports the amount of memory
(BSS and similar) that U-Boot needs to use, but that isn't part of the
binary size. This can be used by the code that loads U-Boot into memory to
determine where to load U-Boot, based on other users of memory.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>
diff --git a/arch/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S
index f385ed4..7a98a1c 100644
--- a/arch/arm/cpu/armv8/start.S
+++ b/arch/arm/cpu/armv8/start.S
@@ -19,7 +19,9 @@
 
 .globl	_start
 _start:
-#ifdef CONFIG_ENABLE_ARM_SOC_BOOT0_HOOK
+#if defined(LINUX_KERNEL_IMAGE_HEADER)
+#include <asm/boot0-linux-kernel-header.h>
+#elif defined(CONFIG_ENABLE_ARM_SOC_BOOT0_HOOK)
 /*
  * Various SoCs need something special and SoC-specific up front in
  * order to boot, allow them to set that in their boot0.h file and then