x86: SGI UV: Add volatile semantics to macros that access chipset registers

Add volatile-semantics to the SGI UV read/write macros that are
used to access chipset memory mapped registers. No direct
references to volatile are made. Instead the readq/writeq macros
are used.

Signed-off-by: Jack Steiner <steiner@sgi.com>
Cc: linux-mm@kvack.org
Cc: dwalker@fifo99.com
Cc: cfriesen@nortel.com
LKML-Reference: <20090910143149.GA14273@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>