net/mlx5e: Support HW (offloaded) and SW counters for SRIOV switchdev mode

Switchdev driver net-device port statistics should follow the model introduced
in commit a5ea31f5 'Merge branch net-offloaded-stats'.

For VF reps we return the SRIOV eswitch vport stats as the usual ones and SW stats
if asked. For the PF, if we're in the switchdev mode, we return the uplink stats
and SW stats if asked, otherwise as before. The uplink stats are implemented using
the PPCNT 802_3 counters which are already being read/cached by the driver.

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>