uboot-imx

rockchip: select DM_USB for rockchip SoC

Select DM_USB to compatible with USB DM driver model.

Signed-off-by: MengDongyang <daniel.meng@rock-chips.com>
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Simon Glass <sjg@chromium.org>