dt-bindings: Clean-up schema indentation formatting

Fix various inconsistencies in schema indentation. Most of these are
list indentation which should be 2 spaces more than the start of the
enclosing keyword. This doesn't matter functionally, but affects running
scripts which do transforms on the schema files.

Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Acked-By: Vinod Koul <vkoul@kernel.org>
Acked-by: Mark Brown <broonie@kernel.org>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Rob Herring <robh@kernel.org>