unify 'cmd_transfer' like 'pio_transfer' and 'dma_transfer' as void
function, and also change left_rx_word according to transfer result.
Signed-off-by: NQipan Li <Qipan.Li@csr.com>
Signed-off-by: NBarry Song <Baohua.Song@csr.com>
Signed-off-by: NMark Brown <broonie@kernel.org>