drm: rcar-du: Release vsp device reference in all error paths

Use drmm_add_action_or_reset() instead of drmm_add_action() to ensure
the vsp device reference is released in case the function call fails.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>