DWC OTG driver. Fix a hang issue when using LOW and FULL speed
BULK traffic. Make sure we don't ask for data in the last
microframe. This allows using devices like USB mice and USB
keyboards connected to the RPI-B.
Suggested by: gonzo @
gone rule. Optimise use of channels so that when a channel
is not ready another channel is used. Instead of using the SOF interrupt
use the system timer to drive the host statemachine. This might
give lower throughput and higher latency, but reduces the CPU usage
significantly. The DWC OTG host mode support should not be considered
for serious USB host controller applications. Some problems are still
seen with LOW speed USB devices.
The DWC OTG host mode support should still be considered
experimental. Isochronous support for DWC OTG is not
fully implemented. Some code added derives from
Aleksandr Rybalko's dotg.c driver.
