x86/platform/uv/BAU: Clean up pq_init()

The payload queue first MMR requires the physical memory address and hub
GNODE of where the payload queue resides in memory, but the associated
variables are named as if the PNODE were used. Rename gnode-related
variables and clarify the definitions of the payload queue head, last, and
tail pointers.

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/1474474161-265604-4-git-send-email-abanman@sgi.com


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