mlxsw: reg: Add Policy-Engine TCAM Allocation Register

The PTAR register is used for allocation of regions in the TCAM.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>