tty/serial: at91: use of_property_read_bool

Use of_property_read_bool to check for the existence of a property.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression e1,e2;
statement S2,S1;
@@
-       if (of_get_property(e1,e2,NULL))
+       if (of_property_read_bool(e1,e2))
        S1 else S2
// </smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/atmel_serial.c

@@ -1635,8 +1635,8 @@ static void atmel_init_property(struct atmel_uart_port *atmel_port,
 
 	if (np) {
 		/* DMA/PDC usage specification */
-		if (of_get_property(np, "atmel,use-dma-rx", NULL)) {
-			if (of_get_property(np, "dmas", NULL)) {
+		if (of_property_read_bool(np, "atmel,use-dma-rx")) {
+			if (of_property_read_bool(np, "dmas")) {
 				atmel_port->use_dma_rx  = true;
 				atmel_port->use_pdc_rx  = false;
 			} else {
@@ -1648,8 +1648,8 @@ static void atmel_init_property(struct atmel_uart_port *atmel_port,
 			atmel_port->use_pdc_rx  = false;
 		}
 
-		if (of_get_property(np, "atmel,use-dma-tx", NULL)) {
-			if (of_get_property(np, "dmas", NULL)) {
+		if (of_property_read_bool(np, "atmel,use-dma-tx")) {
+			if (of_property_read_bool(np, "dmas")) {
 				atmel_port->use_dma_tx  = true;
 				atmel_port->use_pdc_tx  = false;
 			} else {