examples/l3fwd: make route array constant
examples/l3fwd: make route array constant

The initial route setup array is unmodified by the lpm code
and can be made constant. This depends on earlier patch to
fix the rte_lpm6 to use const.

Signed-off-by: Stephen Hemminger <06fa905d7f2aaced6dc72e9511c71a2a51e8aead@networkplumber.org>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk