arm64: memory: rename VA_START to PAGE_END

Prior to commit:

  14c127c957c1c607 ("arm64: mm: Flip kernel VA space")

... VA_START described the start of the TTBR1 address space for a given
VA size described by VA_BITS, where all kernel mappings began.

Since that commit, VA_START described a portion midway through the
address space, where the linear map ends and other kernel mappings
begin.

To avoid confusion, let's rename VA_START to PAGE_END, making it clear
that it's not the start of the TTBR1 address space and implying that
it's related to PAGE_OFFSET. Comments and other mnemonics are updated
accordingly, along with a typo fix in the decription of VMEMMAP_SIZE.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Steve Capper <steve.capper@arm.com>
Reviewed-by: Steve Capper <steve.capper@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 7252222..f87a324 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -226,7 +226,7 @@ void __init kasan_init(void)
 	kasan_map_populate(kimg_shadow_start, kimg_shadow_end,
 			   early_pfn_to_nid(virt_to_pfn(lm_alias(_text))));
 
-	kasan_populate_early_shadow(kasan_mem_to_shadow((void *) VA_START),
+	kasan_populate_early_shadow(kasan_mem_to_shadow((void *)PAGE_END),
 				   (void *)mod_shadow_start);
 	kasan_populate_early_shadow((void *)kimg_shadow_end,
 				   (void *)KASAN_SHADOW_END);