ARM: dts: omap3-beagle: Provide NAND ready pin

On these boards NAND ready pin status is avilable over
GPMC_WAIT0 pin.

For NAND we don't use GPMC wait pin monitoring but
get the NAND Ready/Busy# status using GPIOlib.
GPMC driver provides the WAIT0 pin status over GPIOlib.

Read speed increases from 13212 KiB/ to 15753 KiB/s
and write speed was unchanged at 4404 KiB/s.

Measured using mtd_speedtest.ko on omap3-beagle-c4.
Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/boot/dts/omap3-beagle.dts

@@ -390,6 +390,7 @@ nand@0,0 {
 		interrupts = <0 IRQ_TYPE_NONE>, /* fifoevent */
 			     <1 IRQ_TYPE_NONE>;	/* termcount */
 		ti,nand-ecc-opt = "ham1";
+		rb-gpios = <&gpmc 0 GPIO_ACTIVE_HIGH>; /* gpmc_wait0 */
 		nand-bus-width = <16>;
 		#address-cells = <1>;
 		#size-cells = <1>;