mmc: mtk-sd: add SD/MMC host controller driver for MT7623 SoC

This patch adds MT7623 host controller driver for accessing SD/MMC.

Cc: Jaehoon Chung <jh80.chung@samsung.com>
Tested-by: Matthias Brugger <matthias.bgg@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/mmc/Makefile b/drivers/mmc/Makefile
index 23c5b0d..801a26d 100644
--- a/drivers/mmc/Makefile
+++ b/drivers/mmc/Makefile
@@ -65,3 +65,4 @@
 obj-$(CONFIG_MMC_UNIPHIER)		+= tmio-common.o uniphier-sd.o
 obj-$(CONFIG_RENESAS_SDHI)		+= tmio-common.o renesas-sdhi.o
 obj-$(CONFIG_MMC_BCM2835)		+= bcm2835_sdhost.o
+obj-$(CONFIG_MMC_MTK)			+= mtk-sd.o