clk: imx8mm: Let IMX8MM_CLK_LCDIF_PIXEL set parent rate

clk: imx8mm: Let IMX8MM_CLK_LCDIF_PIXEL set parent rate

By default the display pixel clock needs to be evenly divide
down from 594MHz which rules out a significant number of
resolution and refresh rates.
The current clock tree looks something like:

video_pll1                  594000000
  video_pll1_bypass         594000000
     video_pll1_out         594000000
        lcdif_pixel         148500000

Now that composite-8m supports determine_rate, we can allow
lcdif_pixel to set the parent rate which then switches
every clock in the chain to a new frequency when lcdif_pixel
cannot evenly divide from video_pll1_out.

Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Link: https://lore.kernel.org/r/20230323230127.120883-4-aford173@gmail.com