drm/vc4: hdmi: Add HDMI format detection registers to register list

The block can detect what the incoming image timings are for
debug purposes. Add them to the list of registers understood
by the driver to allow easy dumping of the values.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://lore.kernel.org/r/20220613144800.326124-28-maxime@cerno.tech


Signed-off-by: Maxime Ripard <maxime@cerno.tech>