virtio: rng: Check notifier helpers for VIRTIO_CONFIG_IRQ_IDX

virtio: rng: Check notifier helpers for VIRTIO_CONFIG_IRQ_IDX

Since the driver doesn't support interrupts, we must return early when
index is set to VIRTIO_CONFIG_IRQ_IDX.  Basically the same thing Viresh
did for "91208dd297f2 virtio: i2c: Check notifier helpers for
VIRTIO_CONFIG_IRQ_IDX".

Fixes: 544f0278afca ("virtio: introduce macro VIRTIO_CONFIG_IRQ_IDX")
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Message-Id: <20231025171841.3379663-1-mathieu.poirier@linaro.org>
Tested-by: Leo Yan <leo.yan@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>