ipset: build ip_set_setlist.ko module

Not sure if this was overlooked, or if it is not in a suitable state
for general use, but lets give it a shot and see how it works.

Signed-off-by: Kevin Locke <kevin@kevinlocke.name>

[j.eng: it was overlooked]

extensions/ipset/Kbuild

@@ -3,4 +3,4 @@
 obj-m += ipt_set.o ipt_SET.o
 obj-m += ip_set.o ip_set_ipmap.o ip_set_portmap.o ip_set_macipmap.o
 obj-m += ip_set_iphash.o ip_set_nethash.o ip_set_ipporthash.o
-obj-m += ip_set_iptree.o ip_set_iptreemap.o
+obj-m += ip_set_iptree.o ip_set_iptreemap.o ip_set_setlist.o