drm/tests: connector: Add tests for drmm_connector_hdmi_init

We just introduced a new initialization function for our connectors, so
let's build a kunit test suite for it as well.

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-v15-2-c5af16c3aae2@kernel.org


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