drm/connector: Introduce an HDMI connector initialization function

A lot of the various HDMI drivers duplicate some logic that depends on
the HDMI spec itself and not really a particular hardware
implementation.

Output BPC or format selection, infoframe generation are good examples
of such areas.

This creates a lot of boilerplate, with a lot of variations, which makes
it hard for userspace to rely on, and makes it difficult to get it right
for drivers.

In the next patches, we'll add a lot of infrastructure around the
drm_connector and drm_connector_state structures, which will allow to
abstract away the duplicated logic. This infrastructure comes with a few
requirements though, and thus we need a new initialization function.

Hopefully, this will make drivers simpler to handle, and their behaviour
more consistent.

Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Reviewed-by: Sui Jingfeng <sui.jingfeng@linux.dev>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240527-kms-hdmi-connector-state-v15-1-c5af16c3aae2@kernel.org


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