dt-bindings: gpu: v3d: Add BCM2712's compatible

BCM2712, Raspberry Pi 5's SoC, contains a V3D core. So add its specific
compatible to the bindings.

Signed-off-by: Iago Toral Quiroga <itoral@igalia.com>
Reviewed-by: Maíra Canal <mcanal@igalia.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231031073859.25298-4-itoral@igalia.com