mlxsw: spectrum: Expose counters for various packet sizes

Expose counters ASIC has in the group of RFC 2819 counters that count
number of packets within specific size range.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>