drm/vc4: plane: Register a different drm_plane_helper_funcs on BCM2711

On the BCM2711, our current definition of drm_plane_helper_funcs uses
the custom vc4_prepare_fb() and vc4_cleanup_fb().

Those functions rely on the buffer allocation path that was relying on
the GPU, and is no longer relevant.

Let's create another drm_plane_helper_funcs structure that we will
register on the BCM2711.
Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220610115149.964394-8-maxime@cerno.tech

drivers/gpu/drm/vc4/vc4_plane.c

@@ -1389,6 +1389,13 @@ static const struct drm_plane_helper_funcs vc4_plane_helper_funcs = {
 	.atomic_async_update = vc4_plane_atomic_async_update,
 };
 
+static const struct drm_plane_helper_funcs vc5_plane_helper_funcs = {
+	.atomic_check = vc4_plane_atomic_check,
+	.atomic_update = vc4_plane_atomic_update,
+	.atomic_async_check = vc4_plane_atomic_async_check,
+	.atomic_async_update = vc4_plane_atomic_async_update,
+};
+
 static bool vc4_format_mod_supported(struct drm_plane *plane,
 				     uint32_t format,
 				     uint64_t modifier)
@@ -1493,6 +1500,9 @@ struct drm_plane *vc4_plane_init(struct drm_device *dev,
 	if (ret)
 		return ERR_PTR(ret);
 
+	if (vc4->is_vc5)
+		drm_plane_helper_add(plane, &vc5_plane_helper_funcs);
+	else
 		drm_plane_helper_add(plane, &vc4_plane_helper_funcs);
 
 	drm_plane_create_alpha_property(plane);