drm/radeon: delete radeon_fence_process in is_signaled, no deadlock

Delete the attempt to progress the queue when checking if fence is
signaled. This avoids deadlock.

dma-fence_ops::signaled can be called with the fence lock in unknown
state. For radeon, the fence lock is also the wait queue lock. This can
cause a self deadlock when signaled() tries to make forward progress on
the wait queue. But advancing the queue is unneeded because incorrectly
returning false from signaled() is perfectly acceptable.

Link: https://github.com/brave/brave-browser/issues/49182
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4641
Cc: Alex Deucher <[e-mail]>
Signed-off-by: Robert McClinton <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/radeon/radeon_fence.c

···
 	if (atomic64_read(&rdev->fence_drv[ring].last_seq) >= seq)
 		return true;
 
-	if (down_read_trylock(&rdev->exclusive_lock)) {
-		radeon_fence_process(rdev, ring);
-		up_read(&rdev->exclusive_lock);
-
-		if (atomic64_read(&rdev->fence_drv[ring].last_seq) >= seq)
-			return true;
-	}
 	return false;
 }