iptables: fix wrong depends for nftables support (FS#707)

The dep for the nftables support was wrong, if someone actually enable
that option gain a compilation error. This fix this problem.

Signed-off-by: Ansuel Smith <[email protected]>

package/network/utils/iptables/Makefile

@@ -432,7 +432,7 @@ define Package/libxtables
  ABI_VERSION:=$(PKG_VERSION)
  DEPENDS:= \
 	+IPTABLES_CONNLABEL:libnetfilter-conntrack \
-	+IPTABLES_NFTABLES:libnfnetlink
+	+IPTABLES_NFTABLES:libnftnl
 endef
 
 TARGET_CPPFLAGS := \