dtoverlays: Add invx and invy overrides to ads7846 touch overlay

It had swapxy, but no way to trigger the X and Y inversions

Also use the generic "touchscreen-swapped-x-y" for swapxy
instead of the TI specific "ti,swap-xy".

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>

Author: 6by9

arch/arm/boot/dts/overlays/README

@@ -602,6 +602,8 @@ Params: cs                      SPI bus Chip Select (default 1)
         pmax                    Maximum reported pressure value (default 65535)
         xohms                   Touchpanel sensitivity (X-plate resistance)
                                 (default 400)
+        invx                    Invert x axis
+        invy                    Invert y axis
 
         penirq is required and usually xohms (60-100) has to be set as well.
         Apart from that, pmax (255) and swapxy are also common.

arch/arm/boot/dts/overlays/ads7846-overlay.dts

@@ -77,13 +77,15 @@
 			 <&ads7846>,"interrupts:0",
 			 <&ads7846>,"pendown-gpio:4";
 		penirq_pull = <&ads7846_pins>,"brcm,pull:0";
-		swapxy = <&ads7846>,"ti,swap-xy?";
+		swapxy = <&ads7846>,"touchscreen-swapped-x-y?";
 		xmin =   <&ads7846>,"ti,x-min;0";
 		ymin =   <&ads7846>,"ti,y-min;0";
 		xmax =   <&ads7846>,"ti,x-max;0";
 		ymax =   <&ads7846>,"ti,y-max;0";
 		pmin =   <&ads7846>,"ti,pressure-min;0";
 		pmax =   <&ads7846>,"ti,pressure-max;0";
 		xohms =  <&ads7846>,"ti,x-plate-ohms;0";
+		invx =   <&ads7846>,"touchscreen-inverted-x?";
+		invy =   <&ads7846>,"touchscreen-inverted-y?";
 	};
 };