arm64: mark EFI reserved memory as reserved

The EFI runtime support for arm64 was not reserving EFI_RESERVED_TYPE
memory regions. This leads to potential memory corruption if the kernel
uses that memory and it is also needed by UEFI runtime services.

Signed-off-by: Mark Salter <msalter@redhat.com>
arm64: enter EFI virtual mode from an early_initcall

Signed-off-by: Mark Salter <msalter@redhat.com>
arm64: remove incorrect filepath from comment

Signed-off-by: Mark Salter <msalter@redhat.com>
arm64: have efi stub flush cache by address

Signed-off-by: Mark Salter <msalter@redhat.com>