mmc: rockchip_sdhci: enable strobe line for HS400

The default configuration of rk3399 EMMC PHY does not enable the
strobe line, and EMMC controller will got data transmission error
at HS400 mode.

Signed-off-by: Yifeng Zhao <yifeng.zhao@rock-chips.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/drivers/mmc/rockchip_sdhci.c b/drivers/mmc/rockchip_sdhci.c
index 1ac0058..2784738 100644
--- a/drivers/mmc/rockchip_sdhci.c
+++ b/drivers/mmc/rockchip_sdhci.c
@@ -143,6 +143,9 @@
 	writel(RK_CLRSETBITS(3 << 12, freqsel << 12), &phy->emmcphy_con[0]);
 	writel(RK_CLRSETBITS(1 << 1, 1 << 1), &phy->emmcphy_con[6]);
 
+	/* REN Enable on STRB Line for HS400 */
+	writel(RK_CLRSETBITS(0, 1 << 9), &phy->emmcphy_con[2]);
+
 	read_poll_timeout(readl, &phy->emmcphy_status, dllrdy,
 			  PHYCTRL_DLL_LOCK_WO_TMOUT(dllrdy), 1, 5000);
 }