kernel: kmod-xfrm-interface requires IPv6

The xfrm_interface module will not be built if IPv6 is not enabled in
the kernel. Add this dependency in the kmod package to avoid people
wondering why it doesn't build when they disabled IPv6.

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>

package/kernel/linux/modules/netsupport.mk

@@ -375,7 +375,7 @@ $(eval $(call KernelPackage,ip6-vti))
 define KernelPackage/xfrm-interface
   SUBMENU:=$(NETWORK_SUPPORT_MENU)
   TITLE:=IPsec XFRM Interface
-  DEPENDS:=+kmod-ipsec4 +IPV6:kmod-ipsec6
+  DEPENDS:=@IPV6 +kmod-ipsec4 +kmod-ipsec6
   KCONFIG:=CONFIG_XFRM_INTERFACE
   FILES:=$(LINUX_DIR)/net/xfrm/xfrm_interface.ko
   AUTOLOAD:=$(call AutoProbe,xfrm_interface)