drm/{i915,xe}/display: move irq calls to parent interface

drm/{i915,xe}/display: move irq calls to parent interface

Add an irq parent driver interface for the .enabled and .synchronize
calls. This lets us drop the dependency on i915_drv.h and i915_irq.h in
multiple places, and subsequently remove the compat i915_irq.h and
i915_irq.c files along with the display/ext directory from xe
altogether.

Introduce new intel_parent.[ch] as the wrapper layer to chase the
function pointers and convert between generic and more specific display
types.

v2: Keep static wrappers in intel_display_irq.c (Ville)

v3: Full blown wrappers in intel_parent.[ch] (Ville)

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/dd62dd52ef10d9ecf77da3bdf6a70f71193d141c.1763370931.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>