dt-bindings: display: eliminate yamllint warnings

Eliminate the following yamllint warnings:
./Documentation/devicetree/bindings/display/bridge/analogix,anx7625.yaml
:52:9: [warning] wrong indentation: expected 6 but found 8 (indentation)

./Documentation/devicetree/bindings/display/bridge/intel,keembay-dsi.yaml
:42:8: [warning] wrong indentation: expected 8 but found 7 (indentation)
:45:8: [warning] wrong indentation: expected 8 but found 7 (indentation)

./Documentation/devicetree/bindings/display/intel,keembay-msscam.yaml
:21:6: [warning] wrong indentation: expected 6 but found 5 (indentation)

./Documentation/devicetree/bindings/display/panel/novatek,nt36672a.yaml
:25:10: [warning] wrong indentation: expected 10 but found 9 (indentation)
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201207044830.1551-2-thunder.leizhen@huawei.comSigned-off-by: Rob Herring <robh@kernel.org>