MMC: S3C24XX: Ensure host->mrq->data is valid

Fix a crash if host->mrq->data is NULL on ending a transfer.
Signed-off-by: NBen Dooks <ben-linux@fluff.org>
Signed-off-by: NPierre Ossman <drzeus@drzeus.cx>

drivers/mmc/host/s3cmci.c

@@ -353,7 +353,8 @@ static void pio_tasklet(unsigned long data)
 			    (host->pio_active == XFER_READ) ? "read" : "write",
 			    host->pio_count, host->pio_words);
 
-			host->mrq->data->error = -EINVAL;
+			if (host->mrq->data)
+				host->mrq->data->error = -EINVAL;
 		}
 
 		finalize_request(host);