arm64: Kconfig: support CONFIG_KASAN_VMALLOC

arm64: Kconfig: support CONFIG_KASAN_VMALLOC

We can backed shadow memory in vmalloc area after vmalloc area
isn't populated at kasan_init(), thus make KASAN_VMALLOC selectable.

Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
Acked-by: Andrey Konovalov <andreyknvl@gmail.com>
Tested-by: Andrey Konovalov <andreyknvl@gmail.com>
Tested-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20210324040522.15548-4-lecopzer.chen@mediatek.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>