ASoC: Forward calls to snd_soc_cache_sync() to regcache_sync()

For convenience for drivers that do not want to keep their own pointer to
regmap struct around forward calls to snd_soc_cache_sync() to
regcache_sync() if the driver is using regmap. This is similar to what we do
for snd_soc_read()/snd_soc_write().

This patch also fixes drivers which already have been converted to regmap,
but still use snd_soc_cache_sync() for trying to the sync the cache.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@kernel.org>