u3g: Note range of GOBI devices

Qualcomm makes the GOBI devices, and gobi_loader port supports all the
Qualcomm GOBI 1000 and 2000 devices with the MDM1000 and MDM2000
chipsets. And likely the 3000 as well, though that's not been tested
on FreeBSD.

Submitted by: zarychtam@plan-b.pwste.edu.pl
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