samples: intel_s1000: loopback audio to I2S host

Updated I2S sample app for Intel S1000 CRB to loopback
the audio from host in addition to playing audio out to codec

When AUDIO_PLAY_FROM_HOST=Y, audio from host is both looped back
and played out to codec

When AUDIO_PLAY_FROM_HOST=N, audio from host is looped back and
app generated ones are played out to codec.

Signed-off-by: Sathish Kuttan <sathish.k.kuttan@intel.com>