a52: limit the number of periods for ioplug from slave PCM

a52: limit the number of periods for ioplug from slave PCM

Intel HDMI:

  PERIOD_SIZE: [32 4272000]
  PERIOD_BYTES: [128 17088000]
  PERIODS: [2 32]
  BUFFER_SIZE: [64 8544000]
  BUFFER_BYTES: [256 34176000]

Selected:

  PERIOD_SIZE: 768
  PERIOD_BYTES: 3072
  PERIODS: 32
  BUFFER_SIZE: 24576
  BUFFER_BYTES: 98304

The a52_hw_params() tries to set the big 4271616 buffer size (frames)
for speaker-test which is beyond the maximal slave buffer.

BugLink: https://github.com/alsa-project/alsa-plugins/pull/23
Signed-off-by: Jaroslav Kysela <perex@perex.cz>