Documentation: Improve softlockup_panic= description text

It should say what that <integer> range is and what that integer value
means. I had to look at the code...

Signed-off-by: Borislav Petkov <bp@suse.de>
[jc: changed non-null to nonzero]
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
1 file changed