x86, UV: Improve BAU performance and error recovery

x86, UV: Improve BAU performance and error recovery

- increase performance of the interrupt handler

- release timed-out software acknowledge resources

- recover from continuous-busy status due to a hardware issue

- add a 'throttle' to keep a uvhub from sending more than a
  specified number of broadcasts concurrently (work around the hardware issue)

- provide a 'nobau' boot command line option

- rename 'pnode' and 'node' to 'uvhub' (the 'node' terminology
  is ambiguous)

- add some new statistics about the scope of broadcasts, retries, the
  hardware issue and the 'throttle'

- split off new function uv_bau_retry_msg() from
  uv_bau_process_message() per community coding style feedback.

- simplify the argument list to uv_bau_process_message(), per
  community coding style feedback.

Signed-off-by: Cliff Wickman <cpw@sgi.com>
Cc: linux-mm@kvack.org
Cc: Jack Steiner <steiner@sgi.com>
Cc: Russ Anderson <rja@sgi.com>
Cc: Mike Travis <travis@sgi.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <E1O25Z4-0004Ur-PB@eag09.americas.sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>