spi: dt-bindings: fsl,dspi: Fix example indentation

DTS example in the bindings should be indented with 2- or 4-spaces, so
correct a mixture of different styles to keep consistent 4-spaces.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://patch.msgid.link/20250509112130.123462-3-krzysztof.kozlowski@linaro.org


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