net/usb: Ethernet quirks for the LG-VL600 4G modem

This adds a driver for the CDC Ethernet part of this modem.  The
device's ID is blacklisted in cdc_ether.c and is white-listed in
this new driver because of the quirks needed to make it useful.
The modem's firmware exposes a CDC ACM port for modem control and a
CDC Ethernet port for network data.  The descriptors look fine but
both ports actually are some sort of multiplexers requiring non-
standard headers added/removed from every packet or they get
ignored.  All information is based on a usb traffic log from a
Windows machine.

On the Verizon 4G network I've seen speeds up to 1.1MB/s so far with
this driver, a speed-o-meter site reports 16.2Mbps/10.5Mbps.
Userspace scripts are required to talk to the CDC ACM port.

Signed-off-by: Andrzej Zaborowski <balrogg@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/usb/Makefile b/drivers/net/usb/Makefile
index cac1703..c7ec8a5 100644
--- a/drivers/net/usb/Makefile
+++ b/drivers/net/usb/Makefile
@@ -27,4 +27,5 @@
 obj-$(CONFIG_USB_SIERRA_NET)	+= sierra_net.o
 obj-$(CONFIG_USB_NET_CX82310_ETH)	+= cx82310_eth.o
 obj-$(CONFIG_USB_NET_CDC_NCM)	+= cdc_ncm.o
+obj-$(CONFIG_USB_VL600)		+= lg-vl600.o