ASoC: tegra: use regmap more directly

Stop open-coding the caching of the ctrl registers; instead, use
regmap_update_bits() to update parts of the register from different
places. The removal of the open-coded cache will allow controls to be
created which touch registers, which will be necessary if any of these
modules are converted to CODECs.

Get rid of tegra*_read/write; just call regmap_read/write directly.

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