Btrfs: do not reset bio->bi_ops while writing bio

flush_epd_write_bio() sets bio->bi_opf by itself to honor REQ_SYNC,
but it's not needed at all since bio->bi_opf has set up properly in
both __extent_writepage() and write_one_eb(), and in the case of
write_one_eb(), it also sets REQ_META, which we will lose in
flush_epd_write_bio().

This remove this unnecessary bio->bi_opf setting.
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -4062,9 +4062,6 @@ static void flush_epd_write_bio(struct extent_page_data *epd)
 	if (epd->bio) {
 		int ret;
 
-		bio_set_op_attrs(epd->bio, REQ_OP_WRITE,
-				 epd->sync_io ? REQ_SYNC : 0);
-
 		ret = submit_one_bio(epd->bio, 0, epd->bio_flags);
 		BUG_ON(ret < 0); /* -ENOMEM */
 		epd->bio = NULL;