dm unstripe: support non-power-of-2 chunk size

Address "FIXME: must support non power of 2 chunk_size, dm-stripe.c does".

Bump target version to indicate change.

Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Tested-by: Scott Bauer <Scott.Bauer@intel.com>
Reviewed-by: Scott Bauer <Scott.Bauer@intel.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>