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/drivers/mmc/fsl_esdhc.c b/drivers/mmc/fsl_esdhc.c
index c55eb28..f5d2ccb 100644
--- a/drivers/mmc/fsl_esdhc.c
+++ b/drivers/mmc/fsl_esdhc.c
@@ -319,7 +319,8 @@
 	esdhc_write32(&regs->cmdarg, cmd->cmdarg);
 #if defined(CONFIG_FSL_USDHC)
 	esdhc_write32(&regs->mixctrl,
-	(esdhc_read32(&regs->mixctrl) & 0xFFFFFF80) | (xfertyp & 0x7F));
+	(esdhc_read32(&regs->mixctrl) & 0xFFFFFF80) | (xfertyp & 0x7F)
+			| (mmc->ddr_mode ? XFERTYP_DDREN : 0));
 	esdhc_write32(&regs->xfertyp, xfertyp & 0xFFFF0000);
 #else
 	esdhc_write32(&regs->xfertyp, xfertyp);
@@ -442,7 +443,7 @@
 		if ((sdhc_clk / (div * pre_div)) <= clock)
 			break;
 
-	pre_div >>= 1;
+	pre_div >>= mmc->ddr_mode ? 2 : 1;
 	div -= 1;
 
 	clk = (pre_div << 8) | (div << 4);
@@ -601,6 +602,9 @@
 	}
 
 	cfg->cfg.host_caps = MMC_MODE_4BIT | MMC_MODE_8BIT | MMC_MODE_HC;
+#ifdef CONFIG_SYS_FSL_ESDHC_HAS_DDR_MODE
+	cfg->cfg.host_caps |= MMC_MODE_DDR_52MHz;
+#endif
 
 	if (cfg->max_bus_width > 0) {
 		if (cfg->max_bus_width < 8)