clk: rockchip: add video-related niu clocks as critical on px30

Video-In and -Out interconnect clocks need to stay on all the
time for the peripheral to work and we do not model the actual
interconnect at this point. So mark them as critical for now.

Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Link: https://lore.kernel.org/r/20190917081903.25139-4-heiko@sntech.de