ASoC: Remove WM8994 register cache

Now that the mfd is using the register map cache there's no need for the
CODEC driver to do any register cache management or any funny dances to
interact with the other drivers using the device so just remove the cache
initialisation and volatility information.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/codecs/Makefile

@@ -87,7 +87,7 @@ snd-soc-wm8988-objs := wm8988.o
 snd-soc-wm8990-objs := wm8990.o
 snd-soc-wm8991-objs := wm8991.o
 snd-soc-wm8993-objs := wm8993.o
-snd-soc-wm8994-objs := wm8994.o wm8994-tables.o wm8958-dsp2.o
+snd-soc-wm8994-objs := wm8994.o wm8958-dsp2.o
 snd-soc-wm8995-objs := wm8995.o
 snd-soc-wm9081-objs := wm9081.o
 snd-soc-wm9090-objs := wm9090.o