TAS571x features multiple biquad filters. Their coefficients
are stored in 20-byte registers, which cannot be supported by
regmap.

This patch adds read and write functions for multi-word (32-bit) register
access and mixer controls for the biquads. The multi-word read/write
functions can be used in the future to implement other features like DRC or
output mixer.
Signed-off-by: Petr Kulhavy <brain@jikos.cz>
Signed-off-by: Mark Brown <broonie@kernel.org>