dm vdo recovery-journal: fix sparse 'mixed bitwiseness' warning

Only one user of WRITE_FLAGS so no need to factor it out in an enum
(which causes sparse's 'mixed bitwiseness' warning).  Just use the
flags in the only consumer.

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>