printk: correct timeout comment, neaten MODULE_PARM_DESC

Neaten the MODULE_PARAM_DESC message.
Use 30 seconds in the comment for the zap console locks timeout.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>