ASoC: soc-pcm: cleanup cppcheck warning at soc_get_playback_capture()

ASoC: soc-pcm: cleanup cppcheck warning at soc_get_playback_capture()

This patch cleanups below cppcheck warning.

sound/soc/soc-pcm.c:2578:22: style: The scope of the variable 'codec_dai' can be reduced. [variableScope]
 struct snd_soc_dai *codec_dai;
                     ^
sound/soc/soc-pcm.c:2580:6: style: The scope of the variable 'stream' can be reduced. [variableScope]
 int stream;
     ^

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87r1fkzf2g.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>