net: enetc: rename "mqprio" to "qopt"

To gain access to the larger encapsulating structure which has the type
tc_mqprio_qopt_offload, rename just the "qopt" field as "qopt".

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>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>