mm: Use the new blk_opf_t type

Improve static type checking by using the new blk_opf_t type for block
layer request flags.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jan Kara <jack@suse.cz>
Cc: Stefan Roesch <shr@fb.com>
Cc: NeilBrown <neilb@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20220714180729.1065367-46-bvanassche@acm.orgSigned-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/writeback.h

@@ -101,9 +101,9 @@ struct writeback_control {
 #endif
 };
 
-static inline int wbc_to_write_flags(struct writeback_control *wbc)
+static inline blk_opf_t wbc_to_write_flags(struct writeback_control *wbc)
 {
-	int flags = 0;
+	blk_opf_t flags = 0;
 
 	if (wbc->punt_to_cgroup)
 		flags = REQ_CGROUP_PUNT;