mlxsw: spectrum_router: Use FIB notifications instead of switchdev calls

Until now, in order to offload a FIB entry to HW we use switchdev op.
However that has limits. Mainly in case we need to make the HW aware of
all route prefixes configured in kernel. HW needs to know those in order
to properly trap appropriate packets and pass the to kernel to do
the forwarding. Abort mechanism is now handled within the mlxsw driver.

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