arm64/efi: move virtmap init to early initcall

Now that the create_mapping() code in mm/mmu.c is able to support
setting up kernel page tables at initcall time, we can move the whole
virtmap creation to arm64_enable_runtime_services() instead of having
a distinct stage during early boot. This also allows us to drop the
arm64-specific EFI_VIRTMAP flag.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>