tools: Import Kconfiglib

Kconfiglib is the flexible Python Kconfig parser and library
created by Ulf Magnusson.
(https://github.com/ulfalizer/Kconfiglib

)

This commit imports kconfiglib.py from
commit ce84c22e58fa59cb93679d4ead03c3cd1387965e,
with ISC SPDX-License-Identifier.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>
Cc: Ulf Magnusson <ulfalizer@gmail.com>
Cc: Wolfgang Denk <wd@denx.de>