UBIFS: remove printk

Remove the "UBIFS background thread ubifs_bgd0_0 started" message.
We kill the background thread when we switch to R/O mode, and
start it again whan we switch to R/W mode. OLPC is doing this
many times during boot, and we see this message many times as
well, which is irritating. So just kill the message.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

fs/ubifs/commit.c

@@ -234,8 +234,8 @@ int ubifs_bg_thread(void *info)
 	int err;
 	struct ubifs_info *c = info;
 
-	ubifs_msg("background thread \"%s\" started, PID %d",
-		  c->bgt_name, current->pid);
+	dbg_msg("background thread \"%s\" started, PID %d",
+		c->bgt_name, current->pid);
 	set_freezable();
 
 	while (1) {