dt-bindings: display: bcm2835-vec: Add BCM2711 compatible

The BCM2711 VEC uses a slightly different, incompatible, setup than the
one used for the earlier SoC. Add a new compatible for it.

Signed-off-by: Mateusz Kwiatkowski <kfyatek+publicgit@gmail.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210520150344.273900-3-maxime@cerno.tech