dm raid: select the Kconfig option CONFIG_MD_RAID0

Since the commit 0cf45031 ("dm raid: add support for the MD RAID0
personality"), the dm-raid subsystem can activate a RAID-0 array.
Therefore, add MD_RAID0 to the dependencies of DM_RAID, so that MD_RAID0
will be selected when DM_RAID is selected.

Fixes: 0cf45031 ("dm raid: add support for the MD RAID0 personality")
Cc: stable@vger.kernel.org # v4.2+
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>