scripts: extract_dts_includes: rename arguments for easier reading
scripts: extract_dts_includes: rename arguments for easier reading

Some functions were using y_key and y_val as argument.  This was not
quite easy to read.  Rename argument into more informative versions.

Signed-off-by: Erwan Gouriou <de4d967452b83bb0e37525652734e7d9163b6a4c@linaro.org>

finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,ldts/zephyr,ldts/zephyr,explora26/zephyr,mbolivar/zephyr,explora26/zephyr,explora26/zephyr,kraj/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,zephyriot/zephyr,kraj/zephyr,galak/zephyr,finikorg/zephyr,mbolivar/zephyr,ldts/zephyr,Vudentz/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,zephyriot/zephyr,explora26/zephyr,nashif/zephyr,ldts/zephyr,mbolivar/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,mbolivar/zephyr,galak/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,galak/zephyr,nashif/zephyr,explora26/zephyr,punitvara/zephyr,punitvara/zephyr,Vudentz/zephyr,nashif/zephyr,zephyriot/zephyr,zephyrproject-rtos/zephyr,zephyriot/zephyr,kraj/zephyr,Vudentz/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,punitvara/zephyr,mbolivar/zephyr,Vudentz/zephyr,zephyriot/zephyr,punitvara/zephyr,kraj/zephyr,kraj/zephyr