drm/vc4: hdmi: Use devm to register hotplug interrupts

Commit 776efe80 ("drm/vc4: hdmi: Drop devm interrupt handler for
hotplug interrupts") dropped the device-managed interrupt registration
because it was creating bugs and races whenever an interrupt was coming in
while the device was removed.

However, our latest patches to the HDMI controller driver fix this as well,
so we can use device-managed interrupt handlers again.

Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>