drm/vc4: hdmi: Skip writes to disabled packet RAM

This path actually occurs when audio is started during a hdmi mode set.
As the data will be written by vc4_hdmi_set_infoframes when packet RAM
is enabled again, don't treat as an error

Signed-off-by: Dom Cobley <popcornmix@gmail.com>
Link: https://lore.kernel.org/r/20220613144800.326124-26-maxime@cerno.tech


Signed-off-by: Maxime Ripard <maxime@cerno.tech>