mmc: fsl_esdhc: Add support for DDR mode

Add support of the DDR mode for eSDHC driver.
Enable it for i.MX6 SoC family only.

Signed-off-by: Volodymyr Riazantsev <volodymyr.riazantsev@globallogic.com>
Reviewed-by: York Sun <yorksun@freescale.com>
diff --git a/include/fsl_esdhc.h b/include/fsl_esdhc.h
index c1b6648..313fa1e 100644
--- a/include/fsl_esdhc.h
+++ b/include/fsl_esdhc.h
@@ -108,6 +108,7 @@
 #define XFERTYP_RSPTYP_48_BUSY	0x00030000
 #define XFERTYP_MSBSEL		0x00000020
 #define XFERTYP_DTDSEL		0x00000010
+#define XFERTYP_DDREN		0x00000008
 #define XFERTYP_AC12EN		0x00000004
 #define XFERTYP_BCEN		0x00000002
 #define XFERTYP_DMAEN		0x00000001