drm/vc4: hdmi: Switch to pm_runtime_status_suspended

drm/vc4: hdmi: Switch to pm_runtime_status_suspended

If the controller isn't clocked or its domain powered up, the register
accesses will either stall the CPU or return garbage, respectively.

Thus, we had a warning in our register access function to complain when
that kind of risky accesses were performed.

In order to check the runtime_pm power state, we were using
pm_runtime_active(), but it turns out that it will become active only
once the runtime_resume hook has been executed.

This prevents us from doing any WARN-free register access in our
runtime_resume() implementation, while this is valid.

Let's switch to pm_runtime_status_suspended() instead.

Fixes: b9094a1748e4 ("drm/vc4: hdmi: Warn if we access the controller while disabled")
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://lore.kernel.org/r/20220613144800.326124-23-maxime@cerno.tech
Signed-off-by: Maxime Ripard <maxime@cerno.tech>