drm/vc4: hdmi: Switch to HDMI connector

The new HDMI connector infrastructure allows us to remove a lot of
boilerplate, so let's switch to it.

Acked-by: Sui Jingfeng <sui.jingfeng@linux.dev>
Link: https://patchwork.freedesktop.org/patch/msgid/20240527-kms-hdmi-connector-state-v15-25-c5af16c3aae2@kernel.org


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