tools: fix path handling errors in gen_esp_err_to_name.py for Windows
tools: fix path handling errors in gen_esp_err_to_name.py for Windows

Exclude paths that were specified with slash as a path separator were compared
as strings. This would fail on Windows which uses backslash as a path separator.

espressif/esp-idf,espressif/esp-idf,espressif/esp-idf,espressif/esp-idf