DTS zephyr updates

[AndrewD]

This PR improves the support for indentation so those functions can be reused to generate a nicer Linux DTS. See #1960.

It also changes the formatting of the reg in dts_reg() to be dts schema compliant but I haven't tested if the old format is mandated by zephyr. Can someone please confirm, maybe @maass-hamburg or @trabucayre?

[maass-hamburg]

It also changes the formatting of the reg in dts_reg() to be dts schema compliant but I haven't tested if the old format is mandated by zephyr.

In the zephyr docs it states thats its fine:

Array and similar type property values can be split into several <> blocks

https://docs.zephyrproject.org/latest/build/dts/intro-syntax-structure.html#writing-property-values
the type of reg is array.

[AndrewD]

Thanks for the confirmation and link: my focus has been on other docs.