net: add GSO UDP L4 and GSO fraglists to the list of software-backed types

Commit e20cf8d3f1f7 ("udp: implement GRO for plain UDP sockets.") and
commit 9fd1ff5d2ac7 ("udp: Support UDP fraglist GRO/GSO.") made UDP L4
and fraglisted GRO/GSO fully supported by the software fallback mode.
We can safely add them to NETIF_F_GSO_SOFTWARE to allow logical/virtual
netdevs to forward these types of skbs up to the real drivers.

Signed-off-by: Alexander Lobakin <[e-mail]>
Acked-by: Willem de Bruijn <[e-mail]>
Signed-off-by: Jakub Kicinski <[e-mail]>

include/linux/netdev_features.h

···
 				 NETIF_F_FSO)
 
 /* List of features with software fallbacks. */
-#define NETIF_F_GSO_SOFTWARE	(NETIF_F_ALL_TSO | \
-				 NETIF_F_GSO_SCTP)
+#define NETIF_F_GSO_SOFTWARE	(NETIF_F_ALL_TSO | NETIF_F_GSO_SCTP |	     \
+				 NETIF_F_GSO_UDP_L4 | NETIF_F_GSO_FRAGLIST)
 
 /*
  * If one device supports one of these features, then enable them