dt-bindings: display: Add BCM2712 PixelValve bindings

The BCM2712 has 3 different pixelvalves that are similar to the ones
found in the previous generations but with slightly different
capabilities.

Express that using a new set of compatibles.

Signed-off-by: Maxime Ripard <[e-mail]>
Acked-by: Rob Herring (Arm) <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
Signed-off-by: Dave Stevenson <[e-mail]>

Documentation/devicetree/bindings/display/brcm,bcm2835-pixelvalve0.yaml

···
       - brcm,bcm2711-pixelvalve2
       - brcm,bcm2711-pixelvalve3
       - brcm,bcm2711-pixelvalve4
+      - brcm,bcm2712-pixelvalve0
+      - brcm,bcm2712-pixelvalve1
+      - brcm,bcm2712-pixelvalve2
 
   reg:
     maxItems: 1