timer_stats/doc: Fix /proc/timer_stats documentation

Documentation/timers/timer_stats.txt claims:

"The readout of /proc/timer_stats automatically disables sampling. The sampled
information is kept until a new sample period is started. This allows multiple
readouts."

Some simple testing shows that reading from /proc/timer_stats
does not disable sampling. Looking back over past source code,
it appears that it never did.

Signed-off-by: Michael Kerrisk <[e-mail]>
Cc: Randy Dunlap <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
[ Small tidyup of the changelog. ]
Signed-off-by: Ingo Molnar <[e-mail]>

Documentation/timers/timer_stats.txt

···
 The statistics can be retrieved by:
 # cat /proc/timer_stats
 
-The readout of /proc/timer_stats automatically disables sampling. The sampled
-information is kept until a new sample period is started. This allows multiple
-readouts.
+While sampling is enabled, each readout from /proc/timer_stats will see
+newly updated statistics. Once sampling is disabled, the sampled information
+is kept until a new sample period is started. This allows multiple readouts.
 
 Sample output of /proc/timer_stats: