dts: overlays: vc4-kms-dpi-generic-overlay: Add "interlaced" property

Almost no DPI hardware supports it, but it's useful for RP1 video out.

Signed-off-by: Nick Hollinghurst <[email protected]>

arch/arm/boot/dts/overlays/README

@@ -5099,6 +5099,7 @@ Params: clock-frequency         Display clock frequency (Hz)
         vsync-invert            Vertical sync active low
         de-invert               Data Enable active low
         pixclk-invert           Negative edge pixel clock
+        interlaced              Use an interlaced mode (where supported)
         width-mm                Define the screen width in mm
         height-mm               Define the screen height in mm
         rgb565                  Change to RGB565 output on GPIOs 0-19

arch/arm/boot/dts/overlays/vc4-kms-dpi-generic-overlay.dts

@@ -59,6 +59,7 @@
 		vsync-invert = <&timing>, "vsync-active:0=0";
 		de-invert = <&timing>, "de-active:0=0";
 		pixclk-invert = <&timing>, "pixelclk-active:0=0";
+		interlaced = <&timing>, "interlaced?";
 
 		width-mm = <&panel_generic>, "width-mm:0";
 		height-mm = <&panel_generic>, "height-mm:0";