ASoC: tas2770: Remove unused variables

Remove unused variables in the private struct and the code as these
variables are initially set and then there is no additional code
utilizing these variables.

Signed-off-by: Dan Murphy <dmurphy@ti.com>
Link: https://lore.kernel.org/r/20200923132600.10652-6-dmurphy@ti.com


Signed-off-by: Mark Brown <broonie@kernel.org>