scripts: dtlib: Suppress _init_tokens() pylint warning
scripts: dtlib: Suppress _init_tokens() pylint warning

Suppress this pylint warning so that it can be enabled in the upcoming
CI check. The code is safe.

    scripts/dts/dtlib.py:1904:13: W0631: Using possibly undefined loop
    variable 'i' (undefined-loop-variable)

Also add some more comments to clarify _init_tokens().

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

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