dev-arm: Define ArmInterruptType

dev-arm: Define ArmInterruptType

This is a scoped enum meant to be used mainly in the python world
for DTB autogeneration. By making an ArmInterruptPin self aware of
its own type, we can use it in the C++ world when modelling devices.

For example if a device spec is enforcing a specific triggering behaviour,
its gem5 implementation can query the interrupt type and panic if its
expectations are not met. In this way we are sure what the Linux kernel
sees in the DTB is in sync with how the model really behaves

Change-Id: I66ae3cfbc7b1ed94804f1f882c12eb31f70840da
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/35395
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>