The RTL8156 support CDC NCM mode. And users could set the configuration
of the USB device between vendor and NCM mode dynamically by themselves.
That is, the driver doesn't need to set vendor mode from NCM mode.

Fixes: 195aae32 ("r8152: support new chips")
Signed-off-by: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>