drm/vc4: dpi: Add option for inverting pixel clock and output enable

drm/vc4: dpi: Add option for inverting pixel clock and output enable

[ Upstream commit 3c2707632146b22e97b0fbf6778bab8add2eaa1d ]

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.tech
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Stable-dep-of: 0870d86eac8a ("drm/vc4: dpi: Fix format mapping for RGB565")
Signed-off-by: Sasha Levin <sashal@kernel.org>