r8169: replace open-coded PHY soft reset with genphy_soft_reset

Use genphy_soft_reset() instead of open-coding a PHY soft reset. We have
to do an explicit PHY soft reset because some chips use the genphy driver
which uses a no-op as soft_reset callback.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>