mlxsw: reg: Add Router Algorithmic LPM Tree Allocation Register definition

Register serves for allocation and deallocation of LPM search tree.

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