overlays: add spi override to merus-amp overlay

adds an override to the merus-amp overlay to turn the spi bus off

Change-type: patch
Signed-off-by: Aaron Shaw <shawaj@gmail.com>

arch/arm/boot/dts/overlays/README

@@ -1914,8 +1914,8 @@ Params: speed                   Display SPI bus speed
 
 Name:   merus-amp
 Info:   Configures the merus-amp audio card
-Load:   dtoverlay=merus-amp
-Params: <None>
+Load:   dtoverlay=merus-amp,<param>=<val>
+Params: spioff                  Turn SPI bus off
 
 
 Name:   midi-uart0

arch/arm/boot/dts/overlays/merus-amp-overlay.dts

@@ -57,4 +57,14 @@
 			status = "okay";
 		};
 	};
+
+	fragment@4 {
+		target = <&spi0>;
+		frag4: __overlay__ {
+		};
+	};
+
+	__overrides__ {
+		spioff = <&frag4>, "status=disabled";
+	};
 };