drm/xe/display: Make display suspend/resume work on discrete

We should unpin before evicting all memory, and repin after GT resume.
This way, we preserve the contents of the framebuffers, and won't hang
on resume due to migration engine not being restored yet.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Fixes: dd08ebf6

 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
Cc: stable@vger.kernel.org # v6.8+
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240806105044.596842-3-maarten.lankhorst@linux.intel.com
Signed-off-by: Maarten Lankhorst,,, <maarten.lankhorst@linux.intel.com>
(cherry picked from commit cb8f81c1753187995b7a43e79c12959f14eb32d3)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>