drm/tests: Add HDMI connector rate filter hook tests

drm/tests: Add HDMI connector rate filter hook tests

The previous patch adds a new hook for HDMI connectors to filter out
configurations based on the TMDS character rate. Let's add some tests to
make sure it works as expected.

Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240527-kms-hdmi-connector-state-v15-14-c5af16c3aae2@kernel.org
Signed-off-by: Maxime Ripard <mripard@kernel.org>