usb: device_next: msc: Implement double buffering

Double buffering make it possible to significantly increase the transfer
rates by avoiding idle states. With two SCSI buffers, one buffer can be
used by disk subsystem while the other is being used by UDC (ideally
with DMA).

Signed-off-by: Tomasz Moń <tomasz.mon@nordicsemi.no>
2 files changed