dm mirror log: Use the new blk_opf_t type

Improve static type checking by using the new blk_opf_t type for a function
argument that represents a request operation type.

Cc: Alasdair Kergon <agk@redhat.com>
Cc: Mike Snitzer <snitzer@kernel.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20220714180729.1065367-28-bvanassche@acm.orgSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/dm-log.c

@@ -291,7 +291,7 @@ static void header_from_disk(struct log_header_core *core, struct log_header_dis
 	core->nr_regions = le64_to_cpu(disk->nr_regions);
 }
 
-static int rw_header(struct log_c *lc, int op)
+static int rw_header(struct log_c *lc, enum req_op op)
 {
 	lc->io_req.bi_opf = op;