net/mlx4_core: Allocate default counter per port

Default counter per port will be allocated at the mlx4 core driver load.

Every QP opened by the Ethernet driver will be attached to the port's default
counter.  This is an infrastructure step to collect VF statistics from the PF.

Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Hadar Hen Zion <hadarh@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>