kconfiglib: Update to get split_expr() in

Update Kconfiglib to upstream revision 105c835e70a5b (+ local Zephyr
modifications) to get commit 105c835e70a5b ("Add helper for splitting
expressions") in. It will simplify the 'select' logic in genrest.py and
the upcoming menuconfig implementation, and also simplifies some
Kconfiglib internals.

split_expr() will also be helpful if genrest.py ever needs to split
other expressions, e.g. over multiple lines.

Origin: https://github.com/zephyrproject-rtos/Kconfiglib/tree/zephyr



Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>