omap2/3/4: mailbox: kill compile warning in mailbox.c

Change %d to %ld to avoid the compile warning.
Signed-off-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/mailbox.c

@@ -93,7 +93,7 @@ static int omap2_mbox_startup(struct omap_mbox *mbox)
 
 	mbox_ick_handle = clk_get(NULL, "mailboxes_ick");
 	if (IS_ERR(mbox_ick_handle)) {
-		printk(KERN_ERR "Could not get mailboxes_ick: %d\n",
+		printk(KERN_ERR "Could not get mailboxes_ick: %ld\n",
 			PTR_ERR(mbox_ick_handle));
 		return PTR_ERR(mbox_ick_handle);
 	}