net/enic: support flow counter action

net/enic: support flow counter action

Support counter action for 1400 series adapters.

The adapter API for allocating and freeing counters is independent of
the adapter match/action API. If the filter action is requested, a
counter is first allocated and then assigned to the filter, and when
the filter is deleted, the counter must also be deleted.

Counters are DMAd to pre-allocated consistent memory periodically,
controlled by the define VNIC_FLOW_COUNTER_UPDATE_MSECS. The default is
100 milliseconds.

Signed-off-by: John Daley <johndale@cisco.com>
Reviewed-by: Hyong Youb Kim <hyonkim@cisco.com>