drm/xe: Fix ref counting leak on page fault

If a page fault occurs on VM not in fault a ref can be leaked. Fix this.

Fixes: dd08ebf6

 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240301041036.238471-1-matthew.brost@intel.com


(cherry picked from commit 27b5a3f237fe66dbf2288c2b50973aee8a427e41)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>