ASoC: tas2562: remove useless assignment

ASoC: tas2562: remove useless assignment

cppcheck throws a warning:

sound/soc/codecs/tas2562.c:203:4: style: Assignment of function
parameter has no effect outside the function. [uselessAssignmentArg]
   tx_mask &= ~(1 << right_slot);
   ^

This assignment seems to come from a copy/paste but the value is
indeed not used. Let's remove it.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20210312182246.5153-20-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>