drm/i915: separate display runtime info init

Move display related functionality from intel_device_info_runtime_init()
to intel_display_device_info_runtime_init() and call the latter from the
top level.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/a2226a47a4450e75d867c2ac48665b387af0e42d.1696336887.git.jani.nikula@intel.com