e1000e: cosmetic move of #defines and function prototypes to the new phy.h

Move #defines and function prototypes which are applicable to all/most
devices supported by the driver and are specific to the PHY component of
each device to the new phy.h header file.  These function prototypes can be
used by other files in the driver and moving them to the PHY-specific file
makes it clearer to which component they are applicable.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>