doc: watchdog: modify the explanation related to watchdog thread

"watchdog/%u" threads has be replaced by cpu_stop_work. The current
description is extremely misleading.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Wang Qing <[e-mail]>
Reviewed-by: Petr Mladek <[e-mail]>
Cc: "Guilherme G. Piccoli" <[e-mail]>
Cc: Joe Perches <[e-mail]>
Cc: Jonathan Corbet <[e-mail]>
Cc: Kees Cook <[e-mail]>
Cc: Mauro Carvalho Chehab <[e-mail]>
Cc: Qais Yousef <[e-mail]>
Cc: Randy Dunlap <[e-mail]>
Cc: Santosh Sivaraj <[e-mail]>
Cc: Stephen Kitt <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/admin-guide/lockup-watchdogs.rst

···
 subsystems are present.
 
 A periodic hrtimer runs to generate interrupts and kick the watchdog
-task. An NMI perf event is generated every "watchdog_thresh"
+job. An NMI perf event is generated every "watchdog_thresh"
 (compile-time initialized to 10 and configurable through sysctl of the
 same name) seconds to check for hardlockups. If any CPU in the system
 does not receive any hrtimer interrupt during that time the
···
 generate a kernel warning or call panic, depending on the
 configuration.
 
-The watchdog task is a high priority kernel thread that updates a
+The watchdog job runs in a stop scheduling thread that updates a
 timestamp every time it is scheduled. If that timestamp is not updated
 for 2*watchdog_thresh seconds (the softlockup threshold) the
 'softlockup detector' (coded inside the hrtimer callback function)