mmc: dw_mmc: Fix NULL pointer dereference

If mrq->sbc is not NULL but data->stop happens to be NULL,
it will lead to NULL pointer dereferencing. Avoid this by
having a NULL check for data->stop.

Signed-off-by: Sachin Kamat <[e-mail]>
Acked-by: Seungwon Jeon <[e-mail]>
Signed-off-by: Chris Ball <[e-mail]>

drivers/mmc/host/dw_mmc.c

···
 
 			if (!err) {
 				if (!data->stop || mrq->sbc) {
-					if (mrq->sbc)
+					if (mrq->sbc && data->stop)
 						data->stop->error = 0;
 					dw_mci_request_end(host, mrq);
 					goto unlock;