checkpatch: fix UNNECESSARY_KERN_LEVEL false positive

KERN_<LEVEL> is never redundant with printk_ratelimited or printk_once.
(Except perhaps in the sense that you could use e.g.  pr_err_ratelimited
or pr_err_once, but that would apply to printk as well).

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Andy Whitcroft <apw@canonical.com>
Acked-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>