r8169: PHY power-on fix

Fix extracted from Realtek's driver (8.002.00/20070713) for the PHY
attached to 8111/8168b chipsets.

The check against mac_version is just usual paranoia during the bugfix
period of the kernel cycle. -- FR

Tested on Asus M2A-VM motherboard by Roger So.
No regression on my Asrock 945G DVI either (built-in 8168 + 2x8169).

Signed-off-by: Roger So <roger.so@gmail.com>
Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
Cc: Edward Hsu <edward_hsu@realtek.com.tw>