r8169: prepare for exporting rtl_hw_phy_config

In preperation of factoring out the PHY configuration to a separate
source file this patch:
- avoids accessing rtl8169_private internals by passing the phy_device
  and mac_version as separate parameters
- renames rtl_hw_phy_config to r8169_hw_phy_config to avoid namespace
  clashes with other drivers for Realtek hardware

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>