kthread: add __printf attributes

When commit fbae2d44aa1d ("kthread: add kthread_create_worker*()")
introduced some kthread_create_...() functions which were taking
printf-like parametter, it introduced __printf attributes to some
functions (e.g.  kthread_create_worker()).  Nevertheless some new
functions were forgotten (they have been detected thanks to
-Wmissing-format-attribute warning flag).

Add the missing __printf attributes to the newly-introduced functions in
order to detect formatting issues at build-time with -Wformat flag.

Link: http://lkml.kernel.org/r/20161126193543.22672-1-nicolas.iooss_linux@m4x.org
Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index c1c3e63..4fec8b7 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -175,7 +175,7 @@ __printf(2, 3)
 struct kthread_worker *
 kthread_create_worker(unsigned int flags, const char namefmt[], ...);
 
-struct kthread_worker *
+__printf(3, 4) struct kthread_worker *
 kthread_create_worker_on_cpu(int cpu, unsigned int flags,
 			     const char namefmt[], ...);