mlxsw: reg: Add Router Algorithmic LPM Unicast Entry Register definition

Serves for adding, updating and removing fib entries.

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