usbnet: New driver for QinHeng CH9200 devices

There's a bunch of cheap USB 10/100 devices based on QinHeng chipsets. The
vendor driver supports the CH9100 and CH9200 devices, but the majority of
the code is of the if (ch9100) {} else {} form, with the most significant
difference being that CH9200 provides a real MII interface but CH9100 fakes
one with a bunch of global variables and magic commands. I don't have a
CH9100, so it's probably better if someone who does provides an independent
driver for it. In any case, this is a lightly cleaned up version of the
vendor driver with all the CH9100 code dropped.

Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/Kconfig

@@ -583,4 +583,15 @@ config USB_VL600
 
 	  http://ubuntuforums.org/showpost.php?p=10589647&postcount=17
 
+config USB_NET_CH9200
+	tristate "QingHeng CH9200 USB ethernet support"
+	depends on USB_USBNET
+	select MII
+	help
+	  Choose this option if you have a USB ethernet adapter with a QinHeng
+	  CH9200 chipset.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ch9200.
+
 endif # USB_NET_DRIVERS