Revert "drm/i915/dpt: Make DPT object unshrinkable"

This reverts commit 51064d47.

Now that we forcefully evict all DPT VMAs during suspend
there should be no problem allowing the shrinker to eat
the DPT objects.

Cc: Brian Geffon <bgeffon@google.com>
Cc: Vidya Srinivas <vidya.srinivas@intel.com>
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/12965


Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241127061117.25622-5-ville.syrjala@linux.intel.com


Acked-by: Brian Geffon <bgeffon@google.com>
Reviewed-by: Vidya Srinivas <vidya.srinivas@intel.com>
Tested-by: Vidya Srinivas <vidya.srinivas@intel.com>