usb: use only usb_devinfo() in device_set_usb_desc()

[christos]

Summary

device_set_usb_desc() first tries to fetch device information through
the iInterface descriptor, otherwise it falls back to usb_devinfo().
Since usb_devinfo() is both guaranteed to work, and is more verbose, get
rid of the initial iInterface attempt.

Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks

Test Plan

Device with iInterface. Before:

uaudio0: <Scarlett Solo USB> on usbus0

After:

uaudio0: <Focusrite Scarlett Solo USB, class 239/2, rev 2.00/2.80, addr 6> on usbus0

[markj]

I think this is probably ok. I tried dumping config descriptors from all of my USB devices and most either don't have an interface description, or the one they have is less useful than the generic device information.