netfilter: ipset: add dependency on CONFIG_NETFILTER_NETLINK

When SYSCTL and PROC_FS and NETFILTER_NETLINK are not enabled:

net/built-in.o: In function `try_to_load_type':
ip_set_core.c:(.text+0x3ab49): undefined reference to `nfnl_unlock'
ip_set_core.c:(.text+0x3ab4e): undefined reference to `nfnl_lock'
...

Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>

net/netfilter/ipset/Kconfig

@@ -1,6 +1,7 @@
 menuconfig IP_SET
 	tristate "IP set support"
 	depends on INET && NETFILTER
+	depends on NETFILTER_NETLINK
 	help
 	  This option adds IP set support to the kernel.
 	  In order to define and use the sets, you need the userspace utility