PCM_TX/RX are the same as SNDRV_PCM_STREAM_PLAYBACK/CAPTURE.  Use
them directly.
Signed-off-by: NManuel Lauss <manuel.lauss@googlemail.com>
Acked-by: NRalf Baechle <ralf@linux-mips.org>
Acked-by: NLiam Girdwood <lrg@ti.com>
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>