ARM: dts: aspeed: rainier: System has one SPI NOR

Remove the second as it doesn't exist.
Reviewed-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Joel Stanley <joel@jms.id.au>

arch/arm/boot/dts/aspeed-bmc-ibm-rainier.dts

@@ -656,13 +656,6 @@ flash@0 {
 		spi-max-frequency = <50000000>;
 #include "openbmc-flash-layout-128.dtsi"
 	};
-
-	flash@1 {
-		status = "okay";
-		m25p,fast-read;
-		label = "alt-bmc";
-		spi-max-frequency = <50000000>;
-	};
 };
 
 &spi1 {