drm/vc4: hdmi: Rely on interrupts to handle hotplug

DRM currently polls for the HDMI connector status every 10s, which can
be an issue when we connect/disconnect a display quickly or the device
on the other end only issues a hotplug pulse (for example on EDID
change).

Switch the driver to rely on the internal controller logic for the
BCM2711/RPi4.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210524132018.264396-1-maxime@cerno.tech