Adjust output buffer size and sample rate

Use 4 buffers of 96 frames each = 4 ms at 48 kHz.
Keep the 44.1 kHz -> 48 kHz up-sampler in HAL.
Disable mmap mode and non-IRQ mode; this gives better variance for cycle times.
Reduce number of buffers from 4 to 2, works OK in non-mmap mode but not mmap mode.
Update comments based on code review.
Tested with audio input.
Not yet tested with echo cancellation.

Change-Id: I69db00ab408cd2aad5788d602eb01fc0c7e4e78b
1 file changed