Comment # 9 on bug 1058413 from Takashi Iwai

OK, finally found out the culprit.  It's the missing link power control, and
happens only with Kablylake HDMI.  The upstream doesn't hit it because there
was a code refactoring, while we're based on 4.4.x that misses the stuff.

The fix was merged now to SLE12-SP3 branch and gets merged to openSUSE-42.3
branch as well.  It'll be included in the next kernel update.