x86/platform/uv/BAU: Implement uv4_wait_completion with read_status

UV4 does not employ a software-timeout as in previous generations so a new
wait_completion routine without this logic is required. Certain completion
statuses require the AUX status bit in addition to ERROR and BUSY.

Add the read_status routine to construct the full completion status. Use
read_status in the uv4_wait_completion routine to handle all possible
completion statuses.

Signed-off-by: Andrew Banman <abanman@hpe.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Mike Travis <mike.travis@hpe.com>
Cc: sivanich@hpe.com
Cc: rja@hpe.com
Cc: akpm@linux-foundation.org
Link: http://lkml.kernel.org/r/1489077734-111753-7-git-send-email-abanman@hpe.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>