doc: kernel-parameters.txt: fix documentation of nmi_watchdog parameter

The default behavior of hardlockup depends on the config of
CONFIG_BOOTPARAM_HARDLOCKUP_PANIC.

Fix the description of nmi_watchdog to make it clear.
Suggested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-doc@vger.kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/admin-guide/kernel-parameters.txt

@@ -2836,8 +2836,9 @@
 			0 - turn hardlockup detector in nmi_watchdog off
 			1 - turn hardlockup detector in nmi_watchdog on
 			When panic is specified, panic when an NMI watchdog
-			timeout occurs (or 'nopanic' to override the opposite
-			default). To disable both hard and soft lockup detectors,
+			timeout occurs (or 'nopanic' to not panic on an NMI
+			watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
+			To disable both hard and soft lockup detectors,
 			please see 'nowatchdog'.
 			This is useful when you use a panic=... timeout and
 			need the box quickly up again.