mmc: sd: Remove redundant err assignment from mmc_read_switch

Variable err would be firstly initialized by the return value of
mmc_sd_switch().
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/sd.c

@@ -291,8 +291,6 @@ static int mmc_read_switch(struct mmc_card *card)
 		return 0;
 	}
 
-	err = -EIO;
-
 	status = kmalloc(64, GFP_KERNEL);
 	if (!status)
 		return -ENOMEM;