mmc: cb710: Return err value in cb710_wait_while_busy()

Fixes:

drivers/mmc/host/cb710-mmc.c: In function ‘cb710_wait_while_busy’:
drivers/mmc/host/cb710-mmc.c:182:6: warning: variable ‘err’ set but not
used [-Wunused-but-set-variable]
Signed-off-by: Chris Ball <cjb@laptop.org>
Acked-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>

drivers/mmc/host/cb710-mmc.c

@@ -205,7 +205,7 @@ static int cb710_wait_while_busy(struct cb710_slot *slot, uint8_t mask)
 			"WAIT12: waited %d loops, mask %02X, entry val %08X, exit val %08X\n",
 			limit, mask, e, x);
 #endif
-	return 0;
+	return err;
 }
 
 static void cb710_mmc_set_transfer_size(struct cb710_slot *slot,