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

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

This patch cleanups below cppcheck warning.

sound/soc/soc-pcm.c:446:29: style: The scope of the variable 'pcm_codec' can be reduced. [variableScope]
 struct snd_soc_pcm_stream *pcm_codec, *pcm_cpu;
                            ^
sound/soc/soc-pcm.c:446:41: style: The scope of the variable 'pcm_cpu' can be reduced. [variableScope]
 struct snd_soc_pcm_stream *pcm_codec, *pcm_cpu;
                                        ^

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87tukgzf2p.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>