usb: dwc3: patches for v3.7 merge window

Some much needed changes for our dwc3 driver. First there's a
rework on the ep0 handling due to some Silicon issue we uncovered
which affects all users of this IP core (there's a missing
XferNotReady(DATA) event in some conditions). This issue which
show up as a SETUP transfers which wouldn't complete ever and
we would fail TD 7.06 of the Link Layer Test from USB-IF and
Lecroy's USB3 Exerciser.

We also fix a long standing bug regarding EP0 enable sequencing
where we weren't setting a particular bit (Ignore Sequence
Number). Since we never saw any problems caused by that, it
didn't deserve being sent to stable tree.

On this pull request we also fix Burst Size initialization which
should be done only in SuperSpeed and we were mistakenly setting
Burst Size to the maximum value on non-SuperSpeed mode. Again,
since we never saw any problems caused by that, we're not sending
this patch to stable.

There's also a memory ordering fix regarding usage of bitmaps in
dwc3 driver.

You will also find some sparse warnings fix, a fix for missed
isochronous packets when the endpoint is already busy, and a
fix for synchronization delay on dwc3_stop_active_transfer().