watchdog: Remove softlockup_thresh from Documentation

The old softlockup detector has been replaced with new lockup
detector long ago.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NDon Zickus <dzickus@redhat.com>
Link: http://lkml.kernel.org/r/51959687.9090305@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Documentation/sysctl/kernel.txt

@@ -70,7 +70,6 @@ show up in /proc/sys/kernel:
 - shmall
 - shmmax                      [ sysv ipc ]
 - shmmni
-- softlockup_thresh
 - stop-a                      [ SPARC only ]
 - sysrq                       ==> Documentation/sysrq.txt
 - tainted
@@ -605,15 +604,6 @@ without users and with a dead originative process will be destroyed.
 
 ==============================================================
 
-softlockup_thresh:
-
-This value can be used to lower the softlockup tolerance threshold.  The
-default threshold is 60 seconds.  If a cpu is locked up for 60 seconds,
-the kernel complains.  Valid values are 1-60 seconds.  Setting this
-tunable to zero will disable the softlockup detection altogether.
-
-==============================================================
-
 tainted:
 
 Non-zero if the kernel has been tainted.  Numeric values, which