ARM: dts: rockchip: add rk322x dw-mmc resets

dw-mmc got its reset-properties specified, so add the softresets
for it in rk3228/rk3229.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviwed-by: Shawn Lin <shawn.lin@rock-chips.com>