drm/amdkfd: fix improper return value on error

In function kfd_wait_on_events(), when the call to copy_from_user()
fails, the value of return variable ret is 0. 0 indicates success, which
is inconsistent with the execution status. This patch fixes the bug by
assigning "-EFAULT" to ret when copy_from_user() returns an unexpected
value.

Signed-off-by: Pan Bian <bianpan2016@163.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>

drivers/gpu/drm/amd/amdkfd/kfd_events.c

@@ -739,8 +739,10 @@ int kfd_wait_on_events(struct kfd_process *p,
 		struct kfd_event_data event_data;
 
 		if (copy_from_user(&event_data, &events[i],
-				sizeof(struct kfd_event_data)))
+				sizeof(struct kfd_event_data))) {
+			ret = -EFAULT;
 			goto fail;
+		}
 
 		ret = init_event_waiter(p, &event_waiters[i],
 				event_data.event_id, i);