mlxsw: spectrum_router: Make abort mechanism VR-aware

When the abort mechanism is invoked it binds the first virtual router
(VR) to an LPM tree and inserts a default route to direct packets to the
CPU.

With VRFs, we can have router interfaces (RIFs) bound to multiple VRs,
so we need to make sure packets are trapped from all VRs and not just
the first one.

Upon abort invocation, bind all active VRs to the same LPM tree and
insert a default route in each.

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