uboot-imx

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>