Some legitimate functionality currently requires direct sysfs access
that is not otherwise possible via the android APIs.  Specifically,
isochronous USB transfers require this direct access, without which USB
audio applications would noticibly suffer.

Grant read access to the usb files under /sys/devices to prevent this
regression.

Bug: 28417852
Change-Id: I3424bf3498ffa0eb647a54cc962ab8c54f291728