The current driver maps MQPRIO traffic classes directly 1:1 to the
internal hardware queues (TC0 maps to hardware queue 0, etc).  This
direct mapping requires the internal hardware queues to be reconfigured
from lossless to lossy and vice versa when necessary.  This
involves reconfiguring internal buffer thresholds which is
disruptive and not always reliable.

Implement a new scheme to map TCs to internal hardware queues by
matching up their PFC requirements.  This will eliminate the need
to reconfigure a hardware queue internal buffers at run time.  After
remapping, the NIC is closed and opened for the new TC to hardware
queues to take effect.

This patch only adds the basic mapping logic.
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>