ARM: dts: at91: at91sam9g20ek_common: fix SPI bus unit address

w+arch/arm/dts/at91sam9g20ek_common.dtsi:100.21-104.7: Warning (spi_bus_reg): /ahb/apb/spi@fffc8000/mtd_dataflash@0: SPI bus unit address format error, expected "1"
Signed-off-by: NEugen Hristev <eugen.hristev@microchip.com>

arch/arm/dts/at91sam9g20ek_common.dtsi

@@ -97,7 +97,7 @@
 
 			spi0: spi@fffc8000 {
 				cs-gpios = <0>, <&pioC 11 0>, <0>, <0>;
-				mtd_dataflash@0 {
+				mtd_dataflash@1 {
 					compatible = "atmel,at45", "atmel,dataflash";
 					spi-max-frequency = <15000000>;
 					reg = <1>;