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: NSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: NZhenzhong Duan <zhenzhong.duan@oracle.com>
Reviewed-by: NJoel Fernandes (Google) <joel@joelfernandes.org>
Acked-by: NIngo Molnar <mingo@kernel.org>
Acked-by: NSteven 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: NJonathan Corbet <corbet@lwn.net>