arm64: Promote KERNEL_START/KERNEL_END definitions to a header file

KERNEL_START and KERNEL_END are useful outside head.S, move them to a
header file.
Signed-off-by: NJames Morse <james.morse@arm.com>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

arch/arm64/include/asm/memory.h

@@ -87,6 +87,9 @@
 
 #define TASK_UNMAPPED_BASE	(PAGE_ALIGN(TASK_SIZE / 4))
 
+#define KERNEL_START      _text
+#define KERNEL_END        _end
+
 /*
  * The size of the KASAN shadow region. This should be 1/8th of the
  * size of the entire kernel virtual address space.

arch/arm64/kernel/head.S

@@ -52,9 +52,6 @@
 #error TEXT_OFFSET must be less than 2MB
 #endif
 
-#define KERNEL_START	_text
-#define KERNEL_END	_end
-
 /*
  * Kernel startup entry point.
  * ---------------------------