r8152: disable the ECM mode

There are known issues for switching the drivers between ECM mode and
vendor mode. The interrup transfer may become abnormal. The hardware
may have the opportunity to die if you change the configuration without
unloading the current driver first, because all the control transfers
of the current driver would fail after the command of switching the
configuration.

Although to use the ecm driver and vendor driver independently is fine,
it may have problems to change the driver from one to the other by
switching the configuration. Additionally, now the vendor mode driver
is more powerful than the ECM driver. Thus, disable the ECM mode driver,
and let r8152 to set the configuration to vendor mode and reset the
device automatically.

Signed-off-by: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>