ASoC: Convert WM8903 to direct regmap API usage

Converting to an rbtree cache as regcache doesn't have a flat cache.
Since the top of the register map is fairly sparse this should be an
overall win.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Tested-by: Stephen Warren <swarren@nvidia.com>
1 file changed