netlink: fix potential llentry lock leak in newneigh handler

[rcm]

Summary

The netlink newneigh handler has the potential to leak the lock on
llentry objects in the kernel. This patch (hopefully) reconciles several
paths through the newneigh handler that could result in a lock leak.

Sponsored by: Rubicon Communications, LLC ("Netgate")

[markj]

sys/netlink/route/neigh.c

462

There's no need to set lle here since the next line is a return statement.

[rcm]

sys/netlink/route/neigh.c

462

Ah yes thanks