x86/platform/UV: Fix problem with UV4 Socket IDs not being contiguous

x86/platform/UV: Fix problem with UV4 Socket IDs not being contiguous

Orabug: 25477822

The UV4 Socket IDs are not guaranteed to equate to Node values which
can cause the GAM (Global Addressable Memory) table lookups to fail.
Fix this by using an independent index into the GAM table instead of
the Socket ID to reference the base address.

Tested-by: Frank Ramsay <framsay@sgi.com>
Tested-by: John Estabrook <estabrook@sgi.com>
Signed-off-by: Mike Travis <travis@sgi.com>
Reviewed-by: Dimitri Sivanich <sivanich@sgi.com>
Reviewed-by: Nathan Zimmer <nzimmer@sgi.com>
Cc: Alex Thorlton <athorlton@sgi.com>
Cc: Andrew Banman <abanman@sgi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russ Anderson <rja@sgi.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160801184050.048755337@asylum.americas.sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
(cherry picked from commit 054f621fd5b1c7245710f5d3935c94ce6ae4b3b7)
Signed-off-by: Brian Maly <brian.maly@oracle.com>