net-next:asix:PHY_MODE_RTL8211CL should be 0xC

Use correct value for rtl phy support.
(rtl phy are in AX88178 devices like NWU220G and USB2-ET1000).

Signed-off-by: Allan Chou <allan@asix.com.tw>
Tested-by: Grant Grundler <grundler@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>