ASoC: cs35l56: Remove SDW1 TX5 and TX6

Reduce SDW1 to 4 channels and remove the controls for SDW1
TX5 and TX6.

The TX5 and TX6 channels have been removed from B0 silicon.
There is no need to support them on A1 silicon.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20230418144309.1100721-3-rf@opensource.cirrus.com


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