doc: watchdog: modify the doc related to "watchdog/%u"

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

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

Documentation/admin-guide/sysctl/kernel.rst

@@ -1283,11 +1283,11 @@ This parameter can be used to control the soft lockup detector.
 = =================================
 
 The soft lockup detector monitors CPUs for threads that are hogging the CPUs
-without rescheduling voluntarily, and thus prevent the 'watchdog/N' threads
-from running. The mechanism depends on the CPUs ability to respond to timer
-interrupts which are needed for the 'watchdog/N' threads to be woken up by
-the watchdog timer function, otherwise the NMI watchdog — if enabled — can
-detect a hard lockup condition.
+without rescheduling voluntarily, and thus prevent the 'migration/N' threads
+from running, causing the watchdog work fail to execute. The mechanism depends
+on the CPUs ability to respond to timer interrupts which are needed for the
+watchdog work to be queued by the watchdog timer function, otherwise the NMI
+watchdog — if enabled — can detect a hard lockup condition.
 
 
 stack_erasing