Fixes for McASP and dmaengine_pcm

Merge series from Jai Luthra <j-luthra@ti.com>:

This series fixes two patches:

1. Fix the dmaengine API usage by calling dmaengine_synchronize() after
   dmaengine_terminate_async() when xrun events occur in application
2. Use the McASP AFIFO property from DT to refine the period size,
   instead of hardcoding minimum to 64 samples