usbnet: add _mii suffix to usbnet_set/get_link_ksettings

The generic functions assumed devices provided an MDIO interface (accessed
via older mii code, not phylib). This is true only for genuine ethernet.

Devices with a higher level of abstraction or based on different
technologies do not have MDIO. To support this case, first rename
the existing functions with _mii suffix.

v2: rebased on changed upstream
v3: changed names to clearly say that this does NOT use phylib
v4: moved hunks to correct patch; reworded commmit messages

Signed-off-by : Oliver Neukum <oneukum@suse.com>
Tested-by: Roland Dreier <roland@kernel.org>
Reviewed-by: Grant Grundler <grundler@chromium.org>
Tested-by: Grant Grundler <grundler@chromium.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>