md/raid10: fix set but not used variable in sync_request_write()

Building with W=1 reports the following:

drivers/md/raid10.c: In function ‘sync_request_write’:
drivers/md/raid10.c:2441:21: error: variable ‘d’ set but not used [-Werror=unused-but-set-variable]
 2441 |                 int d;
      |                     ^
cc1: all warnings being treated as errors

Remove the usage of that variable.

Fixes: 752d046 ("md: clean up accounting for issued sync IO")
Signed-off-by: John Garry <[email protected]>
Link: https://lore.kernel.org/linux-raid/[email protected]
Signed-off-by: Yu Kuai <[email protected]>

Author: johnpgarry

drivers/md/raid10.c

@@ -2438,15 +2438,12 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio)
 	 * that are active
 	 */
 	for (i = 0; i < conf->copies; i++) {
-		int d;
-
 		tbio = r10_bio->devs[i].repl_bio;
 		if (!tbio || !tbio->bi_end_io)
 			continue;
 		if (r10_bio->devs[i].bio->bi_end_io != end_sync_write
 		    && r10_bio->devs[i].bio != fbio)
 			bio_copy_data(tbio, fbio);
-		d = r10_bio->devs[i].devnum;
 		atomic_inc(&r10_bio->remaining);
 		submit_bio_noacct(tbio);
 	}