Reformat interrupt tree diagram to be clearer
Reformat interrupt tree diagram to be clearer

Refactor the interrupt tree example diagram so that the natural tree
appears above the interrupt tree. The diagram is clearer that way. Also
change the colours and line styles to be clearer.

Signed-off-by: Grant Likely <9069e6f5a2b566e2674a0ba1e2bf39c12c195fad@linaro.org>

devicetree-org/devicetree-specification,kvekaria/devicetree-specification