b_bytes_copied was pointer with NULL value instead of
plain variable.
NULL pointer was passed to audio_tx_done_cb() and dereference
as well.
Now variable is not a pointer.
Buffer for TX and RX FIFO was not taking into account
size of element leading to out of bound access.
audio_tx_done_type_I_pcm_ff_cb() reported copied bytes was not returning
correct value number if channels was omitted in computation.
Transfer size calculation uses simpler arithmetic.
In several place p_desc_end calculation was not taking into account
that starting pointer (_audiod_itf[idxDriver].p_desc) was pointing
past interface association descriptor.
It would result in accessing random memory.
