kernel: Make kmod-mpls depend on iptunnel in kernel 4.19

This new dependency is needed with kernel 4.19.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

package/kernel/linux/modules/netsupport.mk

@@ -1017,7 +1017,7 @@ $(eval $(call KernelPackage,rxrpc))
 define KernelPackage/mpls
   SUBMENU:=$(NETWORK_SUPPORT_MENU)
   TITLE:=MPLS support
-  DEPENDS:=@!LINUX_3_18
+  DEPENDS:=@!LINUX_3_18 +LINUX_4_19:kmod-iptunnel
   KCONFIG:= \
 	CONFIG_MPLS=y \
 	CONFIG_LWTUNNEL=y \