ASoC: renesas: rz-ssi: Simplify the logic in rz_ssi_stream_is_play()

ASoC: renesas: rz-ssi: Simplify the logic in rz_ssi_stream_is_play()

The code in rz_ssi_stream_is_play() checks whether substream->stream is
different from SNDRV_PCM_STREAM_PLAYBACK and returns the capture
struct rz_ssi_stream in that case. The logic is easier to follow if
substream->stream is compared directly against SNDRV_PCM_STREAM_CAPTURE
and return the capture struct rz_ssi_stream.

Use the conditional operator to simplify the code.

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Link: https://patch.msgid.link/20260119195252.3362486-2-claudiu.beznea.uj@bp.renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>