sysfs: document files in /sys/firmware/sgi_uv/

Document files in /sys/firmware/sgi_uv/.

Signed-off-by: Russ Anderson <[e-mail]>
Cc: Jack Steiner <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Acked-by: Greg Kroah-Hartman <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/ABI/testing/sysfs-firmware-sgi_uv

···
+What:		/sys/firmware/sgi_uv/
+Date:		August 2008
+Contact:	Russ Anderson <[e-mail]>
+Description:
+		The /sys/firmware/sgi_uv directory contains information
+		about the SGI UV platform.
+
+		Under that directory are a number of files:
+
+			partition_id
+			coherence_id
+
+		The partition_id entry contains the partition id.
+		SGI UV systems can be partitioned into multiple physical
+		machines, which each partition running a unique copy
+		of the operating system.  Each partition will have a unique
+		partition id.  To display the partition id, use the command:
+
+			cat /sys/firmware/sgi_uv/partition_id
+
+		The coherence_id entry contains the coherence id.
+		A partitioned SGI UV system can have one or more coherence
+		domain.  The coherence id indicates which coherence domain
+		this partition is in.  To display the coherence id, use the
+		command:
+
+			cat /sys/firmware/sgi_uv/coherence_id