mpls: Refactor how the mpls module is built

This refactoring is needed to allow more than just mpls gso
support to be built into the mpls moddule.
Reviewed-by: Simon Horman <horms@verge.net.au>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/Makefile

@@ -69,7 +69,7 @@ obj-$(CONFIG_BATMAN_ADV)	+= batman-adv/
 obj-$(CONFIG_NFC)		+= nfc/
 obj-$(CONFIG_OPENVSWITCH)	+= openvswitch/
 obj-$(CONFIG_VSOCKETS)	+= vmw_vsock/
-obj-$(CONFIG_NET_MPLS_GSO)	+= mpls/
+obj-$(CONFIG_MPLS)		+= mpls/
 obj-$(CONFIG_HSR)		+= hsr/
 ifneq ($(CONFIG_NET_SWITCHDEV),)
 obj-y				+= switchdev/

net/mpls/Kconfig

 #
 # MPLS configuration
 #
+
+menuconfig MPLS
+	tristate "MultiProtocol Label Switching"
+	default n
+	---help---
+	  MultiProtocol Label Switching routes packets through logical
+	  circuits.  Originally conceved as a way of routing packets at
+	  hardware speeds (before hardware was capable of routing ipv4 packets),
+	  MPLS remains as simple way of making tunnels.
+
+	  If you have not heard of MPLS you probably want to say N here.
+
+if MPLS
+
 config NET_MPLS_GSO
-	tristate "MPLS: GSO support"
+	bool "MPLS: GSO support"
 	help
 	 This is helper module to allow segmentation of non-MPLS GSO packets
 	 that have had MPLS stack entries pushed onto them and thus
 	 become MPLS GSO packets.
+
+endif # MPLS