ARM: dts: at91: sam9x60ek: Use quad mode in the spi-nor flash

Both the QSPI controller and the sst26vf064b flash support
quad mode, enable it.
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20200403061222.1277147-1-tudor.ambarus@microchip.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

arch/arm/boot/dts/at91-sam9x60ek.dts

@@ -579,6 +579,8 @@ flash@0 {
 		compatible = "jedec,spi-nor";
 		reg = <0>;
 		spi-max-frequency = <80000000>;
+		spi-tx-bus-width = <4>;
+		spi-rx-bus-width = <4>;
 		m25p,fast-read;
 
 		at91bootstrap@0 {