scripts: extract_dts_includes: Fix path handling in Windows
scripts: extract_dts_includes: Fix path handling in Windows

When building in Windows, extract_dts_includes.py failed with an
exception on boards that have dts sensor bindings. This was caused by
path handling to search for i2c-device.yaml that worked in Linux, but
not in Windows.

Affected boards were disco_l475_iot1, frdm_k64f, frdm_kw41z, and
hexiwear_k64.

Signed-off-by: Maureen Helm <87a696db5547fa477bda9f9e0f00013c839c14d3@nxp.com>

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