drm/i915: add .fence_priority_display to parent interface

drm/i915: add .fence_priority_display to parent interface

Add .fence_priority_display() to display parent interface, removing a
display dependency on gem/i915_gem_object.h.

This allows us to remove the xe compat gem/i915_gem_object.h.

v2: Don't mix this with the rps interface (Ville)

v3: Rebase

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/c7782862956e3aa59eaeb6dcf80906c1fc063ae1.1763370931.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>