fib: fix dpo-receive address in ip6-ll fibs

fib: fix dpo-receive address in ip6-ll fibs

Need to fill frp_addr for local path, it's used by dpo-receive.
If not, address output can be invalid:

$ sudo vppctl sh ip6-ll fe80::dcad:ff:fe00:3/128
IP6-link-local:loop3, fib_index:2, locks:[IPv6-nd:1, ]
fe80::dcad:ff:fe00:3/128 fib:2 index:55 locks:2
  IPv6-nd refs:1 entry-flags:connected,import,local, src-flags:added,contributing,active,
    path-list:[72] locks:2 flags:shared,local, uPRF-list:58 len:0 itfs:[]
      path:[82] pl-index:72 ip6 weight=1 pref=0 receive:  oper-flags:resolved, cfg-flags:local,glean,
        [@0]: dpo-receive: 8000:100:fe80::dcad:ff on loop3

 forwarding:   unicast-ip6-chain
  [@0]: dpo-load-balance: [proto:ip6 index:57 buckets:1 uRPF:58 to:[0:0]]
    [0] [@2]: dpo-receive: 8000:100:fe80::dcad:ff on loop3

Type: fix
Change-Id: Ib9874c5eac74af789e721098d512a1058cb8e404
Signed-off-by: Vladislav Grishenko <themiron@yandex-team.ru>