OMAP2/3/4: UART: allow in-order port traversal

Use list_add_tail() when adding discovered UART ports.  This is so
traversal using list_for_each_entry() will traverse the list in the
order they were found.
Signed-off-by: NKevin Hilman <khilman@deeprootsystems.com>

arch/arm/mach-omap2/serial.c

@@ -601,7 +601,7 @@ void __init omap_serial_init(void)
 		uart->num = i;
 		p->private_data = uart;
 		uart->p = p;
-		list_add(&uart->node, &uart_list);
+		list_add_tail(&uart->node, &uart_list);
 
 		if (cpu_is_omap44xx())
 			p->irq += 32;