ARM: SoC fix for 5.17, part 4

Here is one last regression fix for 5.17, reverting a patch
that went into 5.16 as a cleanup that ended up breaking
external interrupts on Layerscape chips.

The revert makes it work again, but also reintroduces a
build time warning about the nonstandard DT binding that
will have to be dealt with in the future.