doc: dts: bindings: Document regex support and clean up a bit
doc: dts: bindings: Document regex support and clean up a bit

 - Regexes (e.g. 'pinctrl-.*') are supported in property names in
   bindings, but it was undocumented

 - Remove the mention of 'generation: structure'. The only implemented
   output format is #define's.

 - Clean up the language a bit and move related stuff so that it appears
   together

Signed-off-by: Ulf Magnusson <01743f1c1deb1fe75271d62edb65757d98ac0bcb@nordicsemi.no>

finikorg/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,ldts/zephyr,Vudentz/zephyr,galak/zephyr,galak/zephyr,ldts/zephyr,finikorg/zephyr,Vudentz/zephyr,finikorg/zephyr,nashif/zephyr,ldts/zephyr,finikorg/zephyr,Vudentz/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,Vudentz/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,Vudentz/zephyr