ASoC: Intel: hdac_hdmi: Set ops to NULL on remove

When we unload Skylake driver we may end up calling
hdac_component_master_unbind(), it uses acomp->audio_ops, which we set
in hdmi_codec_probe(), so we need to set it to NULL in hdmi_codec_remove(),
otherwise we will dereference no longer existing pointer.

Signed-off-by: Amadeusz Sławiński <amadeuszx.slawinski@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>