drm/i915/acpi: convert to struct intel_display

Going forward, struct intel_display shall replace struct
drm_i915_private as the main display device data pointer type. Convert
intel_acpi.[ch] to struct intel_display.

Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/465436a3442807b49609fc55c9f652a29f96fd02.1723213547.git.jani.nikula@intel.com


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