Hook the ISP/SAF1761 driver into MIPS kernel builds.
- Update FDT file for BERI DE4 boards.
- Add needed kernel configuration keywords.
- Rename module to saf1761otg so that the device unit number does not
interfere with the hardware ID in dmesg.

Sponsored by:	DARPA, AFRL
Add some more spinlocks to protect the state of the USB transfer
queue. Rename some functions to indicate locking requirements.

MFC after:	1 week
Factor out kernel configuration for DWC OTG FDT attach code.