More dwc3 gadget issues with adb

[John Stultz]

Hey Felipe,
  Last week or so, a change[1] in AOSP to adbd seemingly uncovered
another issue with dwc3 gadget scatter-gather support on HiKey960.

Interestingly it doesn't seem to affect the Dragonboard 845c, which
uses the same dwc3 driver and has had its own issues in the past.

The behavior is the same as we saw last time around with both devices.
After booting the device, running "adb logcat -d" (or really any adb
command that transfers more than a trivial amount of data) on the host
will result in the adb output seeming to stall. Any further adb
invocations to the device will hang indefinitely.

I've captured trace events for before the change (works), after the
change (broken), and after the change with the sg_enabled flag turned
off (which works around the problem).

Let me know if there is anything else useful for me to share.

thanks
-john

[1] https://android.googlesource.com/platform/system/core/+/0871824de6c5b868f2a2e67c9b5673cb2181b4c6

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