hung_task/Documentation: Fix hung_task_warnings description

Improve the documentation on hung_task_warnings.
Signed-off-by: NAaron Tomlin <atomlin@redhat.com>
Link: http://lkml.kernel.org/n/tip-xepjnxzummfDlg9lvhh7Rlzc@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

Documentation/sysctl/kernel.txt

@@ -319,10 +319,11 @@ This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
 
 ==============================================================
 
-hung_task_warning:
+hung_task_warnings:
 
 The maximum number of warnings to report. During a check interval
-When this value is reached, no more the warnings will be reported.
+if a hung task is detected, this value is decreased by 1.
+When this value reaches 0, no more warnings will be reported.
 This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
 
 -1: report an infinite number of warnings.