dt-bindings: gpu: v3d: Add BCM2711's compatible

BCM2711, Raspberry Pi 4's SoC, contains a V3D core. So add its specific
compatible to the bindings.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Reviewed-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220603092610.1909675-2-pbrobinson@gmail.com