dm vdo: fix various blk_opf_t sparse warnings

Use proper blk_opf_t type rather than unsigned int.

Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Susan LeGendre-McGhee <slegendr@redhat.com>
Signed-off-by: Matthew Sakai <msakai@redhat.com>