Add support for "DS Telecom DSU7" Modem

[MooSE]

Hi!

I have a 3G modem, manufactured by "DS Telecom" brand. Model is "DSU7".

After first connect i see in lsusb:

Bus 002 Device 017: ID 05c6:1000 Qualcomm, Inc. Mass Storage Device

In dmesg i see:

[524807.861921] usb 2-1: USB disconnect, device number 20
[524826.496200] usb 2-1: new high-speed USB device number 21 using xhci_hcd
[524826.646489] usb 2-1: New USB device found, idVendor=05c6, idProduct=1000
[524826.646498] usb 2-1: New USB device strings: Mfr=3, Product=2, SerialNumber=4
[524826.646505] usb 2-1: Product: Qualcomm CDMA Technologies MSM
[524826.646511] usb 2-1: Manufacturer: Qualcomm, Incorporated
[524826.646516] usb 2-1: SerialNumber: 351602000025260
[524826.649083] usb-storage 2-1:1.0: USB Mass Storage device detected
[524826.650207] scsi host3: usb-storage 2-1:1.0

After some googling i have solution and i wrote small patch (see attach).