ASoC: fsl: imx-audmix: Fix unused assignment to variable 'ret'

Omit unused initialized value, because 'ret' will be assigined
by the function snd_soc_component_read().

Signed-off-by: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Signed-off-by: Tang Bin <tangbin@cmss.chinamobile.com>
Link: https://lore.kernel.org/r/20200513111408.11452-1-tangbin@cmss.chinamobile.com


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