drm/vc4: hdmi: Handle error case of pm_runtime_resume_and_get

The commit 0f525133 ("drm/vc4: hdmi: Make sure the controller is
powered in detect") introduced the necessary power management handling
to avoid register access while controller is powered down.
Unfortunately it just print a warning if pm_runtime_resume_and_get()
fails and proceed anyway.

This could happen during suspend to idle. So we must assume it is unsafe
to access the HDMI register. So bail out properly.

Fixes: 0f525133 ("drm/vc4: hdmi: Make sure the controller is powered in detect")
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Reviewed-by: Maíra Canal <mcanal@igalia.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240821214052.6800-3-wahrenst@gmx.net