scripts/dts/extract: Rework to extract_{controller,cells}
scripts/dts/extract: Rework to extract_{controller,cells}

Rework extract_{controller,cells} so they aren't recursive.  As part of
this change we take the flat cell array property and build a proper list
based on what the number of cells each element would represent.

Fixes #12724

Signed-off-by: Kumar Gala <a5e5248af4cd4f0ed8c515f61d40a6e2db46a66e@linaro.org>

finikorg/zephyr,nashif/zephyr,explora26/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,Vudentz/zephyr,nashif/zephyr,explora26/zephyr,nashif/zephyr,nashif/zephyr,galak/zephyr,galak/zephyr,galak/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,ldts/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,explora26/zephyr,explora26/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,Vudentz/zephyr,Vudentz/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr