x86: Add sysfs entries for UV v4

Create /sys/firmware/sgi_uv sysfs entries for partition_id and coherence_id.

Signed-off-by: Russ Anderson <rja@sgi.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>