mlxsw: spectrum_router: Adjust placement of FIB abort warning

The recent merge commit bb598c1b ("Merge
git://git.kernel.org/pub/scm/linux/kernel/git/davem/net"

) would cause
the FIB abort warning to fire whenever we flush the FIB tables - either
during module removal or actual abort.

Move it back to its rightful location in the FIB abort function.

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>