ASoC: rt715: Use maple tree register cache

ASoC: rt715: Use maple tree register cache

The rt715 can only support single register read and write operations so
does not benefit from block writes. This means it gets no benefit from
using the rbtree register cache over the maple tree register cache so
convert it to use maple trees instead, it is more modern.

Tested-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230609-asoc-rt-sdw-maple-v1-4-85ee50c93905@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>