ASoC: Intel: sof_pcm512x: make HDMI optional for all platforms

ASoC: Intel: sof_pcm512x: make HDMI optional for all platforms

Make HDMI optional for APL and later platforms. If no HDMI codec
is found on the HDA bus, the graphics side driver is missing or
correct codec driver is not part of kernel build, codec_mask
reflects this and HDMI is disabled. The DSP topology will still
have the links for HDMI, so connect these to dummy codec to avoid
failures in topology loading.

This change also fixes a kernel oops that was triggered if
sof_pcm512x was used with SOF configured to use hdac-hdmi (can be
done via "use_common_hdmi=0" or by selecting
CONFIG_SND_SOC_SOF_HDA_COMMON_HDMI_CODEC=n). This is not a supported
configuration.

Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200312194859.4051-4-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>