MFC r283067, r286118, r285638, r285935, r286778, r286780 and r286802:

• Make the FIFO configuration a bit more flexible for the DWC OTG in

device side mode.

• Limit the number of times we loop inside the DWC OTG poll handler to

avoid starving other fast interrupts. Fix a comment while at it.

• Optimise the DWC OTG host mode driver's transmit path
• Optimise the DWC OTG host mode driver's receive path
• Minor code refactor to avoid duplicating code.
• Handle NYET high speed tokens and predict NAK'ing is up next.
• Fixes for HIGH speed ISOCHRONOUS traffic.