drm: adi_axi_hdmi: Allow to build as a module

Allow the adi_axi_hdmi driver to be built as a module.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Sync dts to latest changes in the PLL init code

Use device tree based init for the PLL clocks.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>