ipv6: Use a more suitable label name

The 'out_timer' label was added in commit 63152fc0 ("[NETNS][IPV6]
ip6_fib - gc timer per namespace") when the timer was allocated on the
heap.

Commit 417f28bb ("netns: dont alloc ipv6 fib timer list") removed
the allocation, but kept the label name.

Rename it to a more suitable name.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>