x86/platform/uv/BAU: Add generic function pointers

Many BAU functions have different implementations depending on the UV
version. Rather than switching on the uvhub_version throughout the driver,
we can define a set of operations for each version. This is especially
beneficial for UV4, which will require many new MMR read/write functions.

Currently, the set of abstracted functions are the same for UV1, UV2, and
UV3. The functions were chosen because each one will have a different
implementation for UV4. Other functions will be added as needed to handle
new implementations or to cleanup the existing differences between UV1,
UV2, and UV3, i.e. read_status and wait_completion.

Signed-off-by: Andrew Banman <abanman@sgi.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Mike Travis <travis@sgi.com>
Acked-by: Dimitri Sivanich <sivanich@sgi.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: akpm@linux-foundation.org
Cc: rja@sgi.com
Link: http://lkml.kernel.org/r/1474474161-265604-6-git-send-email-abanman@sgi.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>