ixgbe: Remove unused define

Remove the Marvell 1145 PHY define as we have never had a device that
supports it and have no plan to in the future.  The existence of this
define has caused confusing on whether or not this PHY was supported
by ixgbe.

Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>