net: dsa: felix: act upon the mqprio qopt in taprio offload

The mqprio queue configuration can appear either through
TC_SETUP_QDISC_MQPRIO or through TC_SETUP_QDISC_TAPRIO. Make sure both
are treated in the same way.

Code does nothing new for now (except for rejecting multiple TXQs per
TC, which is a useless concept with DSA switches).

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Ferenc Fejes <fejes@inf.elte.hu>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>