Only check pfc bits in hang logic if PFC is enabled.  Previously,
if DCB was enabled but PFC was disabled the incorrect pause
bits would be checked.
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Don Skidmore <donald.c.skidmore@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>