drm/tests: Add HDMI connector bpc and format tests

The previous patch added the bpc and format an HDMI connector needs to
be set up with for a given connector state.

Let's add a few tests to make sure it works as expected.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240527-kms-hdmi-connector-state-v15-16-c5af16c3aae2@kernel.org


Signed-off-by: Maxime Ripard <mripard@kernel.org>