Enhanced partition statistics: documentation update

Update the documentation to reflect the change in userspace interface.

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

Documentation/ABI/testing/sysfs-block

@@ -0,0 +1,28 @@
+What:		/sys/block/<disk>/stat
+Date:		February 2008
+Contact:	Jerome Marchand <jmarchan@redhat.com>
+Description:
+		The /sys/block/<disk>/stat files displays the I/O
+		statistics of disk <disk>. They contain 11 fields:
+		 1 - reads completed succesfully
+		 2 - reads merged
+		 3 - sectors read
+		 4 - time spent reading (ms)
+		 5 - writes completed
+		 6 - writes merged
+		 7 - sectors written
+		 8 - time spent writing (ms)
+		 9 - I/Os currently in progress
+		10 - time spent doing I/Os (ms)
+		11 - weighted time spent doing I/Os (ms)
+		For more details refer Documentation/iostats.txt
+
+
+What:		/sys/block/<disk>/<part>/stat
+Date:		February 2008
+Contact:	Jerome Marchand <jmarchan@redhat.com>
+Description:
+		The /sys/block/<disk>/<part>/stat files display the
+		I/O statistics of partition <part>. The format is the
+		same as the above-written /sys/block/<disk>/stat
+		format.