x86/platform/UV: Fix GAM MMR references in the UV x2apic code

x86/platform/UV: Fix GAM MMR references in the UV x2apic code

Along with the fixes in UV4A (rev2) MMRs, the code to access those
MMRs also was modified by the fixes.  UV3, UV4, and UV4A no longer
have compatible setups for Global Address Memory (GAM).

Correct the new mistakes.

Signed-off-by: Mike Travis <mike.travis@hpe.com>
Acked-by: Andrew Banman <abanman@hpe.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dimitri Sivanich <sivanich@hpe.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russ Anderson <rja@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1515440405-20880-6-git-send-email-mike.travis@hpe.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>