Fill in the via address length for the predefined IPv4 and IPv6
explicit-null label routes.
Fixes: f8efb73c97e2 ("mpls: multipath route support") Signed-off-by: Robert Shearman <rshearma@brocade.com> Acked-by: Roopa Prabhu <roopa@cumulusnetworks.com> Signed-off-by: David S. Miller <davem@davemloft.net>