mmc: mediatek: add SD write protect support

use mmc core layer's API to support sd write protect
Signed-off-by: Chaotian Jing <chaotian.jing@mediatek.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/mtk-sd.c

@@ -35,6 +35,7 @@
 #include <linux/mmc/mmc.h>
 #include <linux/mmc/sd.h>
 #include <linux/mmc/sdio.h>
+#include <linux/mmc/slot-gpio.h>
 
 #define MAX_BD_NUM          1024
 
@@ -1452,6 +1453,7 @@ static struct mmc_host_ops mt_msdc_ops = {
 	.pre_req = msdc_pre_req,
 	.request = msdc_ops_request,
 	.set_ios = msdc_ops_set_ios,
+	.get_ro = mmc_gpio_get_ro,
 	.start_signal_voltage_switch = msdc_ops_switch_volt,
 	.card_busy = msdc_card_busy,
 	.execute_tuning = msdc_execute_tuning,