drm/vc4: kms: Register a different drm_mode_config_funcs on BCM2711

On the BCM2711, our current definition of drm_mode_config_funcs uses the
custom vc4_fb_create().

However, that function relies on the buffer allocation path that was
relying on the GPU, and is no longer relevant.

Let's create another drm_mode_config_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/20220610115149.964394-7-maxime@cerno.tech