mpls: Allow mpls_gso and mpls_router to be built as modules

CONFIG_MPLS=m doesn't result in a kernel module being built because it
applies to the net/mpls directory, rather than to .o files.

So revert the MPLS menuitem to being a boolean and make MPLS_GSO and
MPLS_ROUTING tristates to allow mpls_gso and mpls_router modules to be
produced as desired.

Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: NRobert Shearman <rshearma@brocade.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/mpls/Kconfig

@@ -3,7 +3,7 @@
 #
 
 menuconfig MPLS
-	tristate "MultiProtocol Label Switching"
+	bool "MultiProtocol Label Switching"
 	default n
 	---help---
 	  MultiProtocol Label Switching routes packets through logical
@@ -16,14 +16,14 @@ menuconfig MPLS
 if MPLS
 
 config NET_MPLS_GSO
-	bool "MPLS: GSO support"
+	tristate "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.
 
 config MPLS_ROUTING
-	bool "MPLS: routing support"
+	tristate "MPLS: routing support"
 	help
 	 Add support for forwarding of mpls packets.
 

net/mpls/Makefile

@@ -2,4 +2,6 @@
 # Makefile for MPLS.
 #
 obj-$(CONFIG_NET_MPLS_GSO) += mpls_gso.o
-obj-$(CONFIG_MPLS_ROUTING) += af_mpls.o
+obj-$(CONFIG_MPLS_ROUTING) += mpls_router.o
+
+mpls_router-y := af_mpls.o