USB: qcserial: Add support for Quectel EC20 Mini PCIe module

USB: qcserial: Add support for Quectel EC20 Mini PCIe module

It seems like this device has same vendor and product IDs as G2K
devices, but it has different number of interfaces(4 vs 5) and also
different interface layout which makes it currently unusable:

	usbcore: registered new interface driver qcserial
	usbserial: USB Serial support registered for Qualcomm USB modem
	usb 2-1.2: unknown number of interfaces: 5

lsusb output:

	Bus 002 Device 003: ID 05c6:9215 Qualcomm, Inc. Acer Gobi 2000 Wireless
	Device Descriptor:
	  bLength                18
	  bDescriptorType         1
	  bcdUSB               2.00
	  bDeviceClass            0 (Defined at Interface level)
	  bDeviceSubClass         0
	  bDeviceProtocol         0
	  bMaxPacketSize0        64
	  idVendor           0x05c6 Qualcomm, Inc.
	  idProduct          0x9215 Acer Gobi 2000 Wireless Modem
	  bcdDevice            2.32
	  iManufacturer           1 Quectel
	  iProduct                2 Quectel LTE Module
	  iSerial                 0
	  bNumConfigurations      1
	  Configuration Descriptor:
	    bLength                 9
	    bDescriptorType         2
	    wTotalLength          209
	    bNumInterfaces          5
	    bConfigurationValue     1
	    iConfiguration          0
	    bmAttributes         0xa0
	      (Bus Powered)
	      Remote Wakeup
	    MaxPower              500mA

Signed-off-by: Petr Štetiar <ynezz@true.cz>
Cc: stable <stable@vger.kernel.org>
[johan: rename define and add comment ]
Signed-off-by: Johan Hovold <johan@kernel.org>