ASoC: ti: omap-mcbsp: remove useless assignment

sound/soc/ti/omap-mcbsp.c:617:10: style: Variable 'ret' is assigned a
value that is never used. [unreadVariable]
 int ret = 0;
         ^

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Reviewed-by: Chao Song <chao.song@intel.com>
Link: https://lore.kernel.org/r/20220822184239.169757-6-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>