md: select BLOCK_LEGACY_AUTOLOAD

When BLOCK_LEGACY_AUTOLOAD is not enable, mdadm is not able to
activate new arrays unless "CREATE names=yes" appears in
mdadm.conf

As this is a regression we need to always enable BLOCK_LEGACY_AUTOLOAD
for when MD is selected - at least until mdadm is updated and the
updates widely available.

Cc: stable@vger.kernel.org # v5.18+
Fixes: fbdee71b ("block: deprecate autoloading based on dev_t")
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Song Liu <song@kernel.org>