printk: add KERN_DEFAULT loglevel to print_modules()

Several WARN_ON() messages omit the '\n' at the end of the string, which
is a simple (and understandable) error.  The next line printed after
that warning line is usually the current module list, and that printk
does not have a log-level marker - resulting in one long mixed-up line.

Adding this loglevel marker will now avoid this unreadable mess.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>