drm/xe/ggtt: prime ggtt->lock against FS_RECLAIM

Increase the sensitivity of the ggtt->lock by priming it against
FS_RECLAIM, such that allocating memory while holding will result in
lockdep splats.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>