zebra: fix compilation in 32bit platform

zebra: fix compilation in 32bit platform

RTA_PAYLOAD() return value depends on the platform bits.

make[5]: Nothing to be done for 'all-am'.
Making all in zebra
  CC       rt_netlink.o
../../zebra/rt_netlink.c: In function 'netlink_macfdb_change':
../../zebra/rt_netlink.c:1695:63: error: format '%ld' expects argument of type 'long int', but argument 7 has type 'unsigned int' [-Werror=format=]
    "%s family %s IF %s(%u) brIF %u - LLADDR is not MAC, len %ld",
                                                               ^
../../zebra/rt_netlink.c: In function 'netlink_ipneigh_change':
../../zebra/rt_netlink.c:2024:57: error: format '%ld' expects argument of type 'long int', but argument 6 has type 'unsigned int' [-Werror=format=]
      "%s family %s IF %s(%u) - LLADDR is not MAC, len %ld",
                                                         ^

Signed-off-by: Jorge Boncompte <jbonor@gmail.com>