r8169: move napi_disable call and rename rtl8169_hw_reset

rtl8169_hw_reset() meanwhile does more than a hw reset, therefore rename
it to rtl8169_cleanup(). In addition move calling napi_disable() to this
function.

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