net: enetc: act upon mqprio queue config in taprio offload

We assume that the mqprio queue configuration from taprio has a simple
1:1 mapping between prio and traffic class, and one TX queue per TC.
That might not be the case. Actually parse and act upon the mqprio
config.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>