drm/i915: Remove DDC pin sanitation

drm/i915: Remove DDC pin sanitation

Stop with the VBT DDC pin sanitation, and instead just check
that the appropriate DDC pin is still available when initializing
a HDMI connector.

The reason being that we want to start initializing ports in
VBT order to deal with VBTs that declare child devices with
seemingly conflicting ports. As the encoder initialization can
fail for other reasons (at least for eDP+AUX) we can't know
upfront which way the conflicts should be resolved.

Note that the old way of sanitizing gave priority to the last
port declared in the VBT, but now we sort of do the opposite by
favoring the first encoder to successfully initialize. So far
we're not aware of HDMI/DDC use cases where this would matter
but for AUX CH (will be subject to a similar change) there are
known cases where it matters.

Also note that the old code fell back to the platform default DDC
pin if the VBT pin was populated but invalid. That doesn't seem like
such a great idea because the VBT might have later declared another
port using that platform default pin, and so we might just be
creating more DDC pin conflicts here. So lets not second guess the
VBT and simply reject the entire HDMI encoder if the VBT DDC pin is
invalid.

v2: Pimp the commit message (Jani)

Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230630155846.29931-4-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>