arm: dts: rockchip: remove obsolete clock gate definitions

The clock and reset unit is now provided by the rk3188-cru clock driver and thus
the old style definitions of the gate clocks can go away.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-By: Max Schwarz <max.schwarz@online.de>
Tested-By: Max Schwarz <max.schwarz@online.de>