drm/radeon: don't leave fence blocked process on failed GPU reset

Force all fence to signal if GPU reset failed so no process get stuck
on waiting fence.

Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org