On UV4, the destination agent verifies each message by checking the
descriptor qualifier field of the message payload. Messages without this
field set to 0x534749 will cause a hub error to assert. Split
bau_message_payload into uv1_2_3 and uv4 versions to account for the
different payload formats.

Enforce the size of each field by using the appropriate u** integer type.
Replace extraneous comments with KernelDoc comment.
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/1489077734-111753-3-git-send-email-abanman@hpe.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>