dt-bindings: lcdif: Fix constraints for imx8mp

i.MX8MP uses 3 clocks, so soften the restrictions for clocks & clock-names.
This SoC requires a power-domain for this peripheral to use. Add it as
a required property.

Fixes: f5419cb0

 ("dt-bindings: lcdif: Add compatible for i.MX8MP")
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Link: https://lore.kernel.org/r/20221208140840.3227035-1-alexander.stein@ew.tq-group.com
Signed-off-by: Rob Herring <robh@kernel.org>