drivers/net/phy/fixed: do not overwrite addr

phy_device_create(..) sets the addr of phy_device with a sane value.
There is no need overwrite it.

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Reviewed-by: Hannes Schmelzer <oe5hpm@oevsv.at>
Tested-by: Hannes Schmelzer <oe5hpm@oevsv.at>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>