ASoC: cs35l33: Add device tree bindings file for cs35l33

Add device tree bindings file for the cs35l33 8V boosted
class D amplifier.

Signed-off-by: Paul Handrigan <Paul.Handrigan@cirrus.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>