[BUG][playback] Underrun after pause-release on HDA Link pipelines

[tlauda]

There is a random underrun after pause-release sequence done on HDA Link pipelines. Repro rate is under 5%. It shows up during CI tests. It looks like Link DMA doesn't copy anything after release, so DSP has no free space for copying data from buffer.
There are two possibilities that we could check:

1. See if the right Link DMA is started by kernel after release. I remember that we've already had such problem before.
2. Fix sequence of pausing/stopping the pipelines. Kernel should first send pause/stop ipc to the FW and only then deassert stream RUN bit. Doing it other way around can potentially lead to incrementing Gateway FPI by the DSP, when RUN bit is already 0 and such behavior can have undefined consequences.

[tlauda]

@mengdonglin @wenqingfu Could you assign someone to this issue? It's randomly failing CI.

[mengdonglin]

Xiuli is fixing PCM STOP sequence in #1169

But we still need to fix PCM PAUSE sequence for the rendering pipeline here , please see comment:　#1169 (comment)

[mengdonglin]

Pause/release problem on capture is a different issue and tracked by thesofproject/sof#1760