mpls: Fix the openvswitch select of NET_MPLS_GSO

Fix the OPENVSWITCH Kconfig option and old Kconfigs by having
OPENVSWITCH select both NET_MPLS_GSO and MPLSO.

A Kbuild test robot reported that when NET_MPLS_GSO is selected by
OPENVSWITCH the generated .config is broken because MPLS is not
selected.

Cc: Simon Horman <horms@verge.net.au>
Fixes: cec9166c mpls: Refactor how the mpls module is built
Reported-by: Nkbuild test robot <fengguang.wu@intel.com>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Reviewed-by: NSimon Horman <horms@verge.net.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/openvswitch/Kconfig

@@ -6,6 +6,7 @@ config OPENVSWITCH
 	tristate "Open vSwitch"
 	depends on INET
 	select LIBCRC32C
+	select MPLS
 	select NET_MPLS_GSO
 	---help---
 	  Open vSwitch is a multilayer Ethernet switch targeted at virtualized