drm/i915: Beef up SDVO/HDMI port checks

The SDVO code already warns when the port in question doesn't
actually support SDVO. Let's make that also bail the encoder
registration like the generic assert_port_valid() we added.

And add a similar thing for g4x HDMI, mainly because on g4x
itsefl port D only supports DP but not SDVO/HDMI. For the
other platforms the generic port_mask check should actually
be sufficient, but since we're here might as well list the
ports.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230616140820.11726-6-ville.syrjala@linux.intel.com