Similar to DCLK_LCDC on RK3328, the DCLK_VOP on RK3228 is typically
parented by the hdmiphy clk and it is expected that the DCLK_VOP and
hdmiphy clk rate are kept in sync.
Use CLK_SET_RATE_PARENT and CLK_SET_RATE_NO_REPARENT flags, same as used
on RK3328, to make full use of all possible supported display modes.