dm/dm-integrity: Combine request operation and flags

Combine the request operation type and request flags into a single
argument. Improve static type checking by using the enum req_op type for
variables that represent a request operation and the new blk_opf_t type for
variables that represent request flags.

Cc: Alasdair Kergon <agk@redhat.com>
Cc: Mike Snitzer <snitzer@kernel.org>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20220714180729.1065367-27-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>