drm/vc4: kms: Switch to drmm_add_action_or_reset

Even though it was pointed in the review by Daniel, and I thought to have
fixed it while applying the patches, but it turns out I forgot to commit
the fixes in the process. Properly fix it this time.

Fixes: dcda7c28 ("drm/vc4: kms: Add functions to create the state objects")
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20201105135656.383350-2-maxime@cerno.tech