Flex-bytes allows for packet matching based on an offset and value. This
is supported via the ethtool user-def option.  It is specified by providing
an offset followed by a 2 byte match value. Offset is measured from the
start of the MAC address.

The following restrictions apply to flex-bytes. The specified offset must
be an even number and be smaller than 0x1fe.

Example usage:

ethtool -N eth0 flow-type tcp4 src-ip 192.168.0.55 dst-ip 172.16.0.55 \
src-port 12 dst-port 13 user-def 0x10ffff action 32
Signed-off-by: Henry Tieman <henry.w.tieman@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>