checkpatch: warn on logging functions with KERN_<LEVEL>

Warn on probable misuses of logging functions with KERN_<LEVEL>
like pr_err(KERN_ERR "foo\n");

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