edtlib: Improve _interrupt_parent() function

According to the following comment on github
https://github.com/zephyrproject-rtos/zephyr/pull/77900/files#r1750393745
edtlib implementation is partially correct and it is missing two things:

1. If an ancestor has an interrupt-controller or interrupt-map property,
   the walk must terminate.
2. If an interrupt-parent property is found, the linked node must be a
   valid interrupt controller or nexus.

This commit add these checks.

Signed-off-by: Ioannis Damigos <ioannis.damigos.uj@renesas.com>