ipv4/igmp: fix build error if !CONFIG_IP_MULTICAST

ip_sf_list_clear_all() needs to be defined even if !CONFIG_IP_MULTICAST

Fixes: 3580d04a ("ipv4/igmp: fix another memory leak in igmpv3_del_delrec()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>