audio: Calculate proper channel count for bytes per frame

On an SSR, write progress is simulated for PCM tracks
by incrementing bytes written and sleeping for the duration
of the buffer sent from AF. Fix calculation of bytes per
frame used for the increment.

Change-Id: I69a5694ec0e45a0fa7d94416620afea3ad170adb
CRs-Fixed: 1058402
1 file changed