mm: convert printk(KERN_<LEVEL> to pr_<level>

Most of the mm subsystem uses pr_<level> so make it consistent.

Miscellanea:

 - Realign arguments
 - Add missing newline to format
 - kmemleak-test.c has a "kmemleak: " prefix added to the
   "Kmemleak testing" logging message via pr_fmt

Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Tejun Heo <tj@kernel.org>	[percpu]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index c554d17..bfbd709 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -1026,8 +1026,8 @@
 
 	if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
 		return -EFAULT;
-	printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",
-			table->procname);
+	pr_warn_once("%s exported in /proc is scheduled for removal\n",
+		     table->procname);
 
 	*lenp = 2;
 	*ppos += *lenp;