Use pause() in vm_object_deallocate() to yield the CPU to the lock holder

rather than a tsleep() on &proc0.  The only wakeup on &proc0 is intended
to awaken the swapper, not random threads blocked in
vm_object_deallocate().

sys/vm/vm_object.c

@@ -516,7 +516,7 @@ vm_object_deallocate(vm_object_t object)
 					 * priority than the current thread.
 					 * Let the lower priority thread run.
 					 */
-					tsleep(&proc0, PVM, "vmo_de", 1);
+					pause("vmo_de", 1);
 					continue;
 				}
 				/*