ethtool.h: MDI setting support

This change modifies the core ethtool struct to allow a driver to
support setting of MDI/MDI-X state for twisted pair wiring.  This
change uses a previously reserved u8 and should not change any
binary compatibility of ethtool.

Also as per Ben Hutchings' suggestion, the capabilities are
stored in a separate byte so the driver can report if it supports
changing settings.

see thread: http://kerneltrap.org/mailarchive/linux-netdev/2010/11/17/6289820/thread



see ethtool patches titled:
ethtool: allow setting MDI-X state

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
CC: Ben Hutchings <bhutchings@solarflare.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>