Alloc memory to save MCAM 'entry to counter' mapping and since
multiple entries can map to same counter, added counter's reference
count tracking.

Do 'entry to counter' mapping when a entry is being installed
and mbox msg sender requested to configure a counter as well.
Mapping is removed when a entry or counter is being freed or
a explicit mbox msg is received to unmap them.
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>