printk: git rid of [sched_delayed] message for printk_deferred

Commit 458df9fd4815 ("printk: remove separate printk_sched buffers and use
printk buf instead") hardcodes printk_deferred() to KERN_WARNING and
inserts the string "[sched_delayed] " before the actual message.  However
it doesn't take into account the KERN_* prefix of the message, that now
ends up in the middle of the output:

 [sched_delayed] ^a4CE: hpet increased min_delta_ns to 20115 nsec

Fix this by just getting rid of the "[sched_delayed] " scnprintf().  The
prefix is useless since 458df9fd4815 anyway since from that moment
printk_deferred() inserts the message into the kernel printk buffer
immediately.  So if the message eventually gets printed to console, it is
printed in the correct order with other messages and there's no need for
any special prefix.  And if the kernel crashes before the message makes it
to console, then prefix in the printk buffer doesn't make the situation
any better.

Link: http://lkml.org/lkml/2014/9/14/4

Signed-off-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/printk/printk.c

@@ -1679,12 +1679,7 @@ asmlinkage int vprintk_emit(int facility, int level,
 	 * The printf needs to come first; we need the syslog
 	 * prefix which might be passed-in as a parameter.
 	 */
-	if (in_sched)
-		text_len = scnprintf(text, sizeof(textbuf),
-				     KERN_WARNING "[sched_delayed] ");
-
-	text_len += vscnprintf(text + text_len,
-			       sizeof(textbuf) - text_len, fmt, args);
+	text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
 
 	/* mark and strip a trailing newline */
 	if (text_len && text[text_len-1] == '\n') {