mlx5: Add software tx_jumbo_packets counter

This counter will represent transmitted packets which has more than
1518 octets.
The NIC has multiple hardware counters for counting transmitted
packets larger than 1518 octets. Each counter counts the packets
in specific range.
We accumulate those counters to have a single counter.

Approved by: hselasky (mentor)
MFC after: 1 week
Sponsored by: Mellanox Technologies