dt-bindings: display: vc4: Document BCM2711 VC5

The BCM2711 comes with a new VideoCore. Add a compatible for it.

Signed-off-by: Maxime Ripard <[e-mail]>
Tested-by: Chanwoo Choi <[e-mail]>
Tested-by: Hoegeun Kwon <[e-mail]>
Tested-by: Stefan Wahren <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Reviewed-by: Eric Anholt <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/10750[e-mail]

Documentation/devicetree/bindings/display/brcm,bcm2835-vc4.yaml

···
 properties:
   compatible:
     enum:
+      - brcm,bcm2711-vc5
       - brcm,bcm2835-vc4
       - brcm,cygnus-vc4