e1000e: Separate MTP board type from ADP

We have the same LAN controller on different PCH's. Separate MTP board
type from an ADP which will allow for specific fixes to be applied for MTP
platforms.

Signed-off-by: Sasha Neftin <sasha.neftin@intel.com>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>