arm: Clear out isa_traits.hh.

arm: Clear out isa_traits.hh.

Remove unused constants, move the interrupt related constants to
arch/arm/interrupts.hh, move a paging related constant to
arch/arm/pagetable.hh, and get rid of unnecessary includes.

Change-Id: Ide219f7a8515e010c1dd029db2ef22d8f614d8a1
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/33198
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>