Investigate allowing a period smaller than 64 for I2S cards

[gillspice]

• It would be nice to be able to lower the period to at least 32 if not lower, so that we can try lower sample rates with lower periods to get equivalent latency to 96k p64 without as much data, this seems to be set in the ALSA driver.
  Here is the driver for the audio injector: https://github.com/raspberrypi/linux/blob/rpi-4.9.y/sound/soc/bcm/audioinjector-pi-soundcard.c
  Working backwards from that file, it seems like the min buffer size might be set in: snd_pcm_hw_params ?
  Starting from the beginning it looks like the min buffer size starts here:
  https://github.com/raspberrypi/linux/blob/rpi-4.9.y/include/sound/pcm.h
  line 54.
  I don't know how to connect the dots between the two, if that makes sense. If we can find a high level way to change that, ideally without rebuilding the kernel, it would be great.
  It seems like the min buffer size is not explicitly set in the specific soundcard driver for either Fe-pi or Audio Injector, that setting seems to be inherited from a lower level file, that gives me some hope that it is just a default and that they may be able to run with smaller periods if we can figure out how to lower the limit.

https://github.com/raspberrypi/linux/blob/rpi-4.19.y/include/uapi/sound/asound.h line 359 SNDRV_PCM_HW_PARAM_PERIOD_SIZE

Maybe this helps?: https://github.com/raspberrypi/linux/blob/e2d2941326922b63d722ebc46520c3a2287b675f/Documentation/sound/designs/tracepoints.rst