ASoC: wm8974: remove unused variables

ASoC: wm8974: remove unused variables

sound/soc/codecs/wm8974.c:200:38: warning:
 wm8974_aux_boost_controls defined but not used [-Wunused-const-variable=]
sound/soc/codecs/wm8974.c:204:38: warning:
 wm8974_mic_boost_controls defined but not used [-Wunused-const-variable=]

commit 8a123ee2a46d ("ASoC: WM8974 DAPM cleanups")
left behind this, remove them.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20200324070615.16248-1-yuehaibing@huawei.com
Signed-off-by: Mark Brown <broonie@kernel.org>