net/sched: act_mpls: Add softdep on mpls_gso.ko

TCA_MPLS_ACT_PUSH and TCA_MPLS_ACT_MAC_PUSH might be used on gso
packets. Such packets will thus require mpls_gso.ko for segmentation.

v2: Drop dependency on CONFIG_NET_MPLS_GSO in Kconfig (from Jakub and
    David).

Fixes: 2a2ea50 ("net: sched: add mpls manipulation actions to TC")
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Link: https://lore.kernel.org/r/1f6cab15bbd15666795061c55563aaf6a386e90e.1603708007.git.gnault@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Guillaume Nault

net/sched/act_mpls.c

@@ -408,6 +408,7 @@ static void __exit mpls_cleanup_module(void)
 module_init(mpls_init_module);
 module_exit(mpls_cleanup_module);
 
+MODULE_SOFTDEP("post: mpls_gso");
 MODULE_AUTHOR("Netronome Systems <oss-drivers@netronome.com>");
 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("MPLS manipulation actions");