inet: remove (struct uncached_list)->quarantine

inet: remove (struct uncached_list)->quarantine

This list is used to tranfert dst that are handled by
rt_flush_dev() and rt6_uncached_list_flush_dev() out
of the per-cpu lists.

But quarantine list is not used later.

If we simply use list_del_init(&rt->dst.rt_uncached),
this also removes the dst from per-cpu list.

This patch also makes the future calls to rt_del_uncached_list()
and rt6_uncached_list_del() faster, because no spinlock
acquisition is needed anymore.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240604165150.726382-1-edumazet@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>