ASoC: SOF: Intel: Change DMIC load IPC to fixed length

This patch changes the flexible array member pdm[] into a fixed
array of four that is the max. number of stereo PDM controllers
in the current Intel platforms. The change simplifies DMIC DAI
load code and aligns the IPC with other DAI types.

The change is compatible with old and new firmware with similar
change. The ABI minor version is increased due to change in
IPC headers.

Signed-off-by: Seppo Ingalsuo <seppo.ingalsuo@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Link: https://lore.kernel.org/r/20200415202816.934-18-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>