mlxsw: reg: Update RATR to support IP-in-IP tunnels

So far, adjacencies have always been of type Ethernet (with value of 0),
and thus there was no need to explicitly support RATR type. However to
support IP-in-IP adjacencies, this type and a suite of IP-in-IP-specific
attributes need to be added.

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