Fixed the step_size_bytes in the ADPCM Accelerator loop taking into account the varying number of bytes that ADPCM steps by.
Corrected the step size bytes for the start of the DSP accelerator chunk.  Patch by hk.konpie
Merge pull request #1192 from skidau/dsp-acc-loop-adpcm

Fixed the step_size_bytes in the ADPCM Accelerator loop