efi: Accept version 2 of memory attributes table

UEFI v2.10 introduces version 2 of the memory attributes table, which
turns the reserved field into a flags field, but is compatible with
version 1 in all other respects. So let's not complain about version 2
if we encounter it.

Cc: <stable@vger.kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>