ASoC: soc-generic-dmaengine-pcm: cleanup cppcheck warning at dmaengine_copy_user()

This patch cleanups below cppcheck warning.

sound/soc/soc-generic-dmaengine-pcm.c:310:6: style: The scope of the variable 'ret' can be reduced. [variableScope]
 int ret;
     ^

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


Signed-off-by: Mark Brown <broonie@kernel.org>