docs: segmentation-offloads.txt: update for UFO depreciation

UFO is deprecated except for tuntap and packet per 0c19f846,
("net: accept UFO datagrams from tuntap and packet"). Update UFO
docs to reflect this.
Signed-off-by: NDaniel Axtens <dja@axtens.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/networking/segmentation-offloads.txt

@@ -49,6 +49,10 @@ datagram into multiple IPv4 fragments.  Many of the requirements for UDP
 fragmentation offload are the same as TSO.  However the IPv4 ID for
 fragments should not increment as a single IPv4 datagram is fragmented.
 
+UFO is deprecated: modern kernels will no longer generate UFO skbs, but can
+still receive them from tuntap and similar devices. Offload of UDP-based
+tunnel protocols is still supported.
+
 IPIP, SIT, GRE, UDP Tunnel, and Remote Checksum Offloads
 ========================================================