ASoC: neo1973_gta02_wm8753: Remove lm4853_{set,get}_state

This patch drops the lm4853_{set,get}_state functions and the "Amp State Switch"
control.
Those were noops which existed to maintain alsa state file compatibility. Since
the control names have changed due to internal changes in the ASoC core and
state file compatibility was broken anyway it makes sense to drop them.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>