Moved the WARN_ON to BUG_ON, as WARN_ON if hit,
can cause null pointer derefrences
Signed-off-by: NVinod Koul <vinod.koul@intel.com>
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>