kconfiglib: Update to get choice.direct_dep in

Update Kconfiglib to upstream revision 509e374dfcadb (+ local Zephyr
modifications) to get commit 509e374dfcadb ("Add Choice.direct_dep
field") in. It is used by the upcoming Python menuconfig implementation
when displaying information about choices.

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



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