net: phy: Update copyright info

For implementing this driver most of the inputs is
provided by Andrew Lunn.

Updating the driver with Andrew Copy right.
Signed-off-by: NKedareswara rao Appana <appanad@xilinx.com>
Signed-off-by: NAndrew Lunn <andrew@lunn.ch>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/phy/xilinx_gmii2rgmii.c

 /* Xilinx GMII2RGMII Converter driver
  *
  * Copyright (C) 2016 Xilinx, Inc.
+ * Copyright (C) 2016 Andrew Lunn <andrew@lunn.ch>
  *
+ * Author: Andrew Lunn <andrew@lunn.ch>
  * Author: Kedareswara rao Appana <appanad@xilinx.com>
  *
  * Description: