Add basic sample rate conversion to the CXD56 Spresense audio
driver using libsamplerate. Currently conversion is only done
during playback and all output is fixed at 48 kHz.
Issues:
- 16 kHz SRC has glitches (unless data dump is enabled)
- 44.1 kHz SRC gets stuck
Signed-off-by: Alin Jerpelea <alin.jerpelea@sony.com>
