mmc: openpiton: add piton_mmc driver

This commit adds support to piton_mmc driver for OpenPiton-riscv64
This driver has many things set as preconfigured because the hardware
automatically configures most of the settings during startup.

Signed-off-by: Tianrui Wei <tianrui-wei@outlook.com>
Signed-off-by: Jonathan Balkind <jbalkind@ucsb.edu>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
diff --git a/drivers/mmc/Kconfig b/drivers/mmc/Kconfig
index 0909f50..d017617 100644
--- a/drivers/mmc/Kconfig
+++ b/drivers/mmc/Kconfig
@@ -727,6 +727,15 @@
 	bool
 	depends on MMC_SUNXI
 
+config MMC_PITON
+	bool "MMC support for OpenPiton SoC"
+	depends on DM_MMC && BLK
+	help
+	  This selects support for the SD host controller on OpenPiton SoC.
+	  Note that this SD controller directly exposes the contents of the
+	  SD card as memory mapped, so there is no manual configuration
+	  required
+
 config GENERIC_ATMEL_MCI
 	bool "Atmel Multimedia Card Interface support"
 	depends on DM_MMC && BLK && ARCH_AT91