ASoC: ti: davinci-mcasp: Add asynchronous mode

Merge series from Sen Wang <sen@ti.com>:

This series adds asynchronous mode support to the McASP driver, which
enables independent configuration of bitclocks, frame sync, and audio
configurations between tx(playback) and rx(record). And achieves
simultaneous playback & record using different audio configurations.

It also adds two clean up patches to the McASP driver that disambiguate
and simplifies the logic which avoids the async enhancement from being
too convoluted to review and analyze.

The implementation is based on vendor documentation and patches tested in
both SK-AM62P-LP (sync mode, McASP slave) and AM62D-EVM
(async mode, McASP master, rx & tx has different TDM configs).
Testing verifies async mode functionality while maintaining backward
compatibility with the default sync mode.

Bootlog and Async mode tests on AM62D-EVM: [0]

[0]: https://gist.github.com/SenWang125/f31f9172b186d414695e37c8b9ef127d