MFC r261795:
Issue doorbell twice before finally freeing the DMA descriptors. This
should fix DMA descriptor caching issues seen with the EHCI controller
found in Google Chromebook C720 during removal and insertion of USB
devices.
MFC r261541, r261543 and r261544:
Import USB RNDIS driver to FreeBSD from OpenBSD.
Useful for so-called USB tethering.
- Imported code from OpenBSD
- Adapted code to FreeBSD
- Removed some unused functions
- Fixed some buffer encoding and decoding issues
- Optimised data transport path a bit, by sending multiple packets at a time
- Increased receive buffer to 16K