drm/xe: Cancel pending TLB inval workers on teardown

Add a new _fini() routine on the GT TLB invalidation
side to handle this worker cleanup on driver teardown.

v2: Move the TLB teardown to the gt fini() routine called during
    gt_init rather than in gt_alloc. This way the GT structure stays
    alive for while we reset the TLB state.

Signed-off-by: Stuart Summers <stuart.summers@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20250826182911.392550-3-stuart.summers@intel.com