ASoC: codecs: max98088: Moved the EX Limiter Mode from dapm widget to control

Moved the EX Limiter Mode from dapm widget to control, because it was not
required DAPM route.

Signed-off-by: Jin Park <jinyoungp@nvidia.com>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>