dts: rk3399: enable dwmmc for sdcard

rk3399 sdcard is using dwmmc controller, enable it for sdcard.
SCLK_SDMMC is the clock for controller operation clock, move it
to the first place.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/dts/rk3399-evb.dts b/arch/arm/dts/rk3399-evb.dts
index bbcfcd0..e92a492 100644
--- a/arch/arm/dts/rk3399-evb.dts
+++ b/arch/arm/dts/rk3399-evb.dts
@@ -61,6 +61,10 @@
 	status = "okay";
 };
 
+&sdmmc {
+	status = "okay";
+};
+
 &sdhci {
 	bus-width = <8>;
 	mmc-hs400-1_8v;