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: James Morse <james.morse@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index f412f50..72a3025 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/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.