samples: i2s_codec: Refine sample for samll RAM platforms

- Configure BLOCK count by using kconfig option
'EXTRA_BLOCKS' instad of fixed value. This allows user to
customize the RAM usage based on their platform.
- Keep the PCM data in flash to avoid large RAM usage.
- Refine the sample to get the SAMPLE_BIT_WIDTH
and BYTES_PER_SAMPLE from Kconfig options.

Signed-off-by: Zhaoxiang Jin <Zhaoxiang.Jin_1@nxp.com>
3 files changed