mmc: dw_mmc: Add support DW SD/MMC driver on SOCFPGA

Add platform specific functionality for the DW SD/MMC driver for
SoCFPGA. Move SDMMC_CMD_USE_HOLD_REG to dw_mmc.h so other platforms
can use this define.

Signed-off-by: Dinh Nguyen <dinguyen@altera.com>
Reviewed-by: Pavel Machek <pavel@denx.de>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Seungwon Jeon <tgih.jun@samsung.com
Signed-off-by: Chris Ball <cjb@laptop.org>
diff --git a/drivers/mmc/host/dw_mmc.h b/drivers/mmc/host/dw_mmc.h
index 2f52c87..81b2994 100644
--- a/drivers/mmc/host/dw_mmc.h
+++ b/drivers/mmc/host/dw_mmc.h
@@ -111,6 +111,7 @@
 #define SDMMC_INT_ERROR			0xbfc2
 /* Command register defines */
 #define SDMMC_CMD_START			BIT(31)
+#define SDMMC_CMD_USE_HOLD_REG	BIT(29)
 #define SDMMC_CMD_CCS_EXP		BIT(23)
 #define SDMMC_CMD_CEATA_RD		BIT(22)
 #define SDMMC_CMD_UPD_CLK		BIT(21)