ASoC: pxa: remove useless assignment

cppcheck warning:

sound/soc/pxa/mmp-pcm.c:207:10: style: Variable 'ret' is assigned a
value that is never used. [unreadVariable]
 int ret = 0, stream;
         ^

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20210326215927.936377-8-pierre-louis.bossart@linux.intel.com


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