DRM provides flags for inverting pixel clock and output enable
signals, but these were not mapped to the relevant registers.

Add those mappings.
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://lore.kernel.org/r/20220613144800.326124-10-maxime@cerno.techSigned-off-by: Maxime Ripard <maxime@cerno.tech>