To enable DPIB/posbuf pointer mode for SKL+ platforms, we need:
- refine BDL settings.
- add pointer callback to read postion from DPIB/posbuf;
- add Kconfig to force IPC update mode on SKL+, that is:
for SKL-, we will always use IPC update mode;
for SKL+, we will use DPIB/posbuf by default, but be able to force IPC mode for debug.