Use the flex filter mechanism to extend the current ethtool filter
operations by intercoperating the user data. This allows to match
eight more bytes within a Ethernet frame in addition to macs, ether
types and vlan.

The matching pattern looks like this:

 * dest_mac [6]
 * src_mac [6]
 * tpid [2]
 * vlan tci [2]
 * ether type [2]
 * user data [8]

This can be used to match Profinet traffic classes by FrameID range.

Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Tested-by: Dvora Fuxbrumer <dvorax.fuxbrumer@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>