A variety of fixes:

    - Resolves some problems with DMA chaining.  It should stream
      a lot better now; but not all the funky cases are handled yet.

    - Now "use_dma_chaining" is a module parameter not a #define.
      It also defaults to false.  Some gadget drivers will work fine
      with this enabled, getting some IRQ reduction and increased
      I/O parallelism (given deep I/O queues); others won't.

    - Handle isochronous transfers (from Mark Huang at Broadcom)

    - Some of the chiprev 0100 workarounds weren't quite right.
      Neither were buffer allocations on dma-incoherent systems.

    - Handle bulk endpoint halts better, for file_storage gadget driver.

    - Handle the hardware device status bits better:
        * selfpowered by default, clearable with the API;
        * remote wakeup disabled by default, host must enable it.

    - Fix a shutdown problem seen in some statically linked configs.

Needed to use the new file_storage gadget without disabling DMA.