ASoC: soc-pcm: Allocate PCM operations dynamically to support multiple DAIs

The original code does not cover the case that two DAIs(CPU) have different
ASoC core PCM operations(like mmap, pointer...). Currently we have only one
global soc_pcm_ops for ASoC core PCM operation. When two DAIs have different
pointer functions, second DAI's pointer function is set for both first DAI
and second DAI in case of original code.

This patch uses runtime's pcm_ops instead of global pcm_ops for each DAIs. So
each DAIs can have different ASoC core PCM operations. This is needed to
support multiple DAIs.

Signed-off-by: Sangsu Park <sangsu4u.park@samsung.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>