drm/i915/ddi: convert intel_ddi.c to struct intel_display

Going forward, struct intel_display is the main display device data
pointer. Convert as much as possible of intel_ddi.c to struct
intel_display.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://lore.kernel.org/r/44aebcf93b2211e917b2ee725433b1f9b5e4e6f6.1742906146.git.jani.nikula@intel.com


Signed-off-by: Jani Nikula <jani.nikula@intel.com>