docs: Add tunnel support to TSO GRE documentation.

Previously support for tunnels was added to userspace TSO. However, the
documentation was not updated appropriately. This patch adds VxLAN and
Geneve as supported tunnels.

Fixes: 084c808 ("userspace: Support VXLAN and GENEVE TSO.")
Acked-by: David Marchand <david.marchand@redhat.com>
Signed-off-by: Mike Pattrick <mkp@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

Author: mkp-rh

Documentation/topics/userspace-tso.rst

@@ -109,9 +109,9 @@ then started again. OvS will then report::
 Limitations
 ~~~~~~~~~~~
 
-The current OvS userspace `TSO` implementation supports flat and VLAN networks
-only (i.e. no support for `TSO` over tunneled connection [VxLAN, GRE, IPinIP,
-etc.]).
+The current OvS userspace `TSO` implementation supports flat, VLAN networks,
+and some tunneled connections.  Currently only VxLAN and Geneve tunnels are
+supported.
 
 The NIC driver must support and advertise checksum offload for TCP and UDP.
 However, SCTP is not mandatory because very few drivers advertised support
@@ -120,11 +120,12 @@ in Open vSwitch. Currently, if the NIC supports that, then the feature is
 enabled, otherwise TSO can still be enabled but SCTP packets sent to the NIC
 will be dropped.
 
-There is no software implementation of TSO, so all ports attached to the
-datapath must support TSO or packets using that feature will be dropped
-on ports without TSO support.  That also means guests using vhost-user
-in client mode will receive TSO packet regardless of TSO being enabled
-or disabled within the guest.
+There is no software implementation of TSO in conjunction with tunnels.  So
+when VxLAN or Geneve tunnels are in use, all ports attached to the datapath
+must support TSO or packets using this combination of features will be dropped
+on ports without hardware TSO support.  That also means guests using
+vhost-user in client mode will receive TSO packet regardless of TSO being
+enabled or disabled within the guest.
 
 All kernel devices that use the raw socket interface (veth, for example)
 require the kernel commit 9d2f67e43b73 ("net/packet: fix packet drop as of