drm/radeon/kms: fix return value from fence function.

We only want to return here for errors, the wait functions return
a positive timeout otherwise, which gets back to userspace and
causes X to crash here.

Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon_fence.c

@@ -197,7 +197,7 @@ retry:
 		r = wait_event_interruptible_timeout(rdev->fence_drv.queue,
 				radeon_fence_signaled(fence), timeout);
 		radeon_irq_kms_sw_irq_put(rdev);
-		if (unlikely(r != 0))
+		if (unlikely(r < 0))
 			return r;
 	} else {
 		radeon_irq_kms_sw_irq_get(rdev);