net/mlx5e: Avoid reset netdev stats on configuration changes

Move all RQ, SQ and channel counters from the channel objects into the
priv structure.  With this change, counters will not be reset upon
channel configuration changes.

Channel's statistics for SQs which are associated with TCs higher than
zero will be presented in ethtool -S, only for SQs which were opened at
least once since the module was loaded (regardless of their open/close
current status).  This is done in order to decrease the total amount of
statistics presented and calculated for the common out of box use (no
QoS).

mlx5e_channel_stats is a compound of CH,RQ,SQs stats in order to
create locality for the NAPI when handling TX and RX of the same
channel.

Align the new statistics struct per ring to avoid several channels
update to the same cache line at the same time.
Packet rate was tested, no degradation sensed.

Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
CC: Qing Huang <qing.huang@oracle.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>