drm/i915/display: Make display responsible for probing its own IP

Rather than selecting the display IP and feature flags at the same time
the general PCI probing happens, move this step into the display code
itself so that it can be more easily re-used outside of i915 (i.e., by
the Xe driver).

v2:
 - Make intel_display_device_probe() always return a non-NULL pointer
   and simplify copying of runtime_defaults.  (Andrzej)
v3:
 - Redefine INTEL_VGA_DEVICE/INTEL_QUANTA_DEVICE to eliminate a cast and
   an include of linux/mod_devicetable.h.  (Jani)
 - Keep explicit memcpy for runtime defaults.  (Jani)

Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230523195609.73627-5-matthew.d.roper@intel.com