net: phy: dp83848: Fix sysfs naming collision warning

Files in sysfs are created using the name from the phy_driver struct,
when two names are the same we may get a duplicate filename warning,
fix this.

Reported-by: kernel test robot <ying.huang@linux.intel.com>
Signed-off-by: Andrew F. Davis <afd@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>