This patch creates sof_apl_hdmi.m4 to define topology for 3 playback
pipelines, FE and BE links for HDMI/DisplayPort(DP) audio. This can be
a reference to verify audio over HDMI/DP on APL platforms.
The HDMI/DP frontends are named as HDMIx, to reuse the generic HDA DSP
machine driver which checks the link names and will do extra
initialization on HDMI/DP frontends if "HDMI" is found in the link name.
This m4 does't include topology for using external HD-A analog codecs. We
will create another m4 file to include both HDA display and analog audio.
Signed-off-by: Mengdong Lin <mengdong.lin@linux.intel.com>