ASoC: wcd-mbhc-v2: remove useless initialization

ASoC: wcd-mbhc-v2: remove useless initialization

cppcheck warning:

sound/soc/codecs/wcd-mbhc-v2.c:1309:17: style: Variable 'clamp_state'
is assigned a value that is never used. [unreadVariable]
 u8 clamp_state = 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: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Link: https://lore.kernel.org/r/20220520211719.607543-4-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>