clk: imx: imx6sx: Allow a different LCDIF1 clock parent

clk: imx: imx6sx: Allow a different LCDIF1 clock parent

It is not a good idea to hardcode the LCDIF1 parent inside the
clock driver because some users may want to use a different clock
parent for LCDIF1. One of the reasons could be related to EMI tests.

Remove the harcoded LCDIF1 parent when the LCDIF1 parent is described
via devicetree.

Old dtb's that do not describe the LCDIF1 parent via devicetree will
use the same PLL5 clock as parent to keep the original behavior.

Signed-off-by: Fabio Estevam <festevam@denx.de>
Reviewed-by: Abel Vesa <abel.vesa@linaro.org>
Link: https://lore.kernel.org/r/20230815130923.775117-1-festevam@gmail.com
Signed-off-by: Abel Vesa <abel.vesa@linaro.org>