net: Do not wrap sysctl igmp_max_memberships in IP_MULTICAST

controlling igmp_max_membership is useful even when IP_MULTICAST
is off.
Quagga(an OSPF deamon) uses multicast addresses for all interfaces
using a single socket and hits igmp_max_membership limit when
there are 20 interfaces or more.
Always export sysctl igmp_max_memberships in proc, just like
igmp_max_msf

Signed-off-by: Joakim Tjernlund <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv4/sysctl_net_ipv4.c

···
 		.mode		= 0644,
 		.proc_handler	= proc_do_large_bitmap,
 	},
-#ifdef CONFIG_IP_MULTICAST
 	{
 		.procname	= "igmp_max_memberships",
 		.data		= &sysctl_igmp_max_memberships,
···
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec
 	},
-
-#endif
 	{
 		.procname	= "igmp_max_msf",
 		.data		= &sysctl_igmp_max_msf,