overlays: Fix mcp23017's addr parameter

The addr parameter of the mcp23017 overlay was broken by the addition
of the noints parameter; splitting the mcp node in two without also
modifying the second half from the addr parameter would cause the two
halves to separate. Change the implementation strategy to patch
fragment 2 (as was originally proposed). This will prevent the
overlay from being applied at runtime until the "dtoverlay" command
is improved, but the overlay already has this restriction due to
fragment 3 so this isn't a step backwards.

See: #3449

Signed-off-by: Phil Elwell <[email protected]>

arch/arm/boot/dts/overlays/mcp23017-overlay.dts

@@ -48,15 +48,13 @@
 	};
 
 	fragment@4 {
-		target = <&i2c1>;
-		__overlay__ {
-			mcp23017_irq: mcp@20 {
-				#interrupt-cells=<2>;
-				interrupt-parent = <&gpio>;
-				interrupts = <4 2>;
-				interrupt-controller;
-				microchip,irq-mirror;
-			};
+		target = <&mcp23017>;
+		mcp23017_irq: __overlay__ {
+			#interrupt-cells=<2>;
+			interrupt-parent = <&gpio>;
+			interrupts = <4 2>;
+			interrupt-controller;
+			microchip,irq-mirror;
 		};
 	};