rtla: fix a example in rtla-timerlat-hist.rst

The following error message is reported when running the example in document.

# timerlat hist -d 10m -c 0-4 -P d:100us:1ms -p 1ms --no-aa
Failed to set timerlat period
Could not apply config

The unit of the period is microsecond, '1ms' cannot be accepted.

usage: [rtla] timerlat hist [-h] [-q] [-d s] [-D] [-n] [-a us] [-p us] [-i us] [-T us] [-s us] ...
...
-p/--period us: timerlat period in us
...

Also fix another minor missleading comment.

Link: https://lore.kernel.org/lkml/[e-mail]

Signed-off-by: Xie XiuQi <[e-mail]>
Signed-off-by: Daniel Bristot de Oliveira <[e-mail]>

Documentation/tools/rtla/rtla-timerlat-hist.rst

···
 In the example below, **rtla timerlat hist** is set to run for *10* minutes,
 in the cpus *0-4*, *skipping zero* only lines. Moreover, **rtla timerlat
 hist** will change the priority of the *timerlat* threads to run under
-*SCHED_DEADLINE* priority, with a *10us* runtime every *1ms* period. The
+*SCHED_DEADLINE* priority, with a *100us* runtime every *1ms* period. The
 *1ms* period is also passed to the *timerlat* tracer. Auto-analysis is disabled
 to reduce overhead ::
 
-  [root@alien ~]# timerlat hist -d 10m -c 0-4 -P d:100us:1ms -p 1ms --no-aa
+  [root@alien ~]# timerlat hist -d 10m -c 0-4 -P d:100us:1ms -p 1000 --no-aa
   # RTLA timerlat histogram
   # Time unit is microseconds (us)
   # Duration:   0 00:10:00