ASoC: topology: ABI - Add flags and private data to PCM

This is the remaining update to PCM ABI object of version 5.

The flags will be applied to FE (Front End) links and can also be used
by physical links. The private data is reserved for future extension, so
offset update will add the private data size.

Now user space is using ABI v4, and the previous patch "ASoC: topology:
make PCM backward compatible from ABI v4" can assure the backward
compatibility.

Signed-off-by: Mengdong Lin <mengdong.lin@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>