doc: add transfer rules VXLAN actions in sfc guide
doc: add transfer rules VXLAN actions in sfc guide

Actions VXLAN_DECAP and VXLAN_ENCAP need to be listed
among actions supported for transfer flows.

Fixes: 6ab6c40d1e83 ("net/sfc: support action VXLAN decap in transfer rules")
Fixes: 1bbd1ec2348a ("net/sfc: support action VXLAN encap in MAE backend")
Cc: stable@dpdk.org

Signed-off-by: Ivan Malov <436a2feb05eb79a6862681e66bd0193220e8fb2d@oktetlabs.ru>
Reviewed-by: Andrew Rybchenko <4155e7bf8e0185127625dac6d84336299844982f@oktetlabs.ru>
Reviewed-by: Andy Moreton <adbee5d9b6a6a553b71b14302d03837591e26c9d@xilinx.com>

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