octeontx2-af: Support for NPC MCAM counters

NPC HW has counters which can be mapped to MCAM
entries to gather entry match statistics. This
patch adds support to allocate, free, clear and retrieve
stats of NPC MCAM counters. New mailbox messages have
been added for this. Similar to MCAM entries both
contiguous and non-contiguous counter allocation is
supported.

Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>