commit 042745ee upstream.

Commit 3a0f9aae ("dm raid: round region_size to power of two")
intended to make sure that the default region size is a power of two.
However, the logic in that commit is incorrect and sets the variable
region_size to 0 or 1, depending on whether min_region_size is a power
of two.

Fix this logic, using roundup_pow_of_two(), so that region_size is
properly rounded up to the next power of two.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: 3a0f9aae ("dm raid: round region_size to power of two")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>