drm/xe/display: Add Xe implementation for fence checks used by fbc code

Xe doesn't support legacy fences. Implement legacy fence and fence
id checks accordingly.

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drm/xe/display: Add empty define for i915_ggtt_clear_scanout

Add empty define for i915_ggtt_clear_scanout to avoid build failure.

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drm/xe/display: Implement display support

As for display, the intent is to share the display code with the i915
driver so that there is maximum reuse there.

We do this by recompiling i915/display code twice.
Now that i915 has been adapted to support the Xe build, we can add
the xe/display support.

This initial work is a collaboration of many people and unfortunately
this squashed patch won't fully honor the proper credits.
But let's try to add a few from the squashed patches:

Co-developed-by: Matthew Brost <matthew.brost@intel.com>
Co-developed-by: Jani Nikula <jani.nikula@intel.com>
Co-developed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Co-developed-by: Matt Roper <matthew.d.roper@intel.com>
Co-developed-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Co-developed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Co-developed-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>