net: enetc: report statistics counters for taprio

Report the "win_drop" counter from the unstructured ethtool -S as
TCA_TAPRIO_OFFLOAD_STATS_WINDOW_DROPS to the Qdisc layer. It is
available both as a global counter as well as a per-TC one.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>