drm/i915: Try to initialize DDI/ICL+ DSI ports for every VBT child device

Try to deal with duplicate child devices for the same DDI port
by attempting to initialize them in VBT defined order The first
on to succeed for a specific DDI port will be the one we use.

We'll also get rid of i915->display.vbt.ports[] here as any conflicts
will now be handled at encoder registration time rather than during
VBT parsing. Note that intel_bios_encoder_data_lookup() still remaims
for pre-DDI DP/HDMI ports as those don't (at least yet) use VBT
driven initialization.

TODO: DSI dual link handling is sketchy at best

v2: Leave intel_bios_encoder_port() to the encoder callback (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/20230630155846.29931-7-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>

drm/i915/dsi: split out icl_dsi.h

Follow the convention of corresponding .h for .c.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211122111504.223248-4-jani.nikula@intel.com