system-arm: Add irq for hypervisor timer in device tree

ARM fast model CPU cannot get timer interrupts without this IRQ setting
in the device tree.

Change-Id: I084c475c04285f4f40eb38a80ddd038207e4764f
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/19650
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

system-arm: Split the VExpress_GEM5_V1 base dts

With the introduction of the new DPU model, we need different
variations of the VExpress_GEM5_V1 platform. This splits the platform
dtsi file into a separate file for the base platform and the
HDLCD-based platform. This matches the hierarchy in RealView.py.

Change-Id: Id02380122655b5d3aa3548a703fdef178bba17d9
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Ciro Santilli <ciro.santilli@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/11035
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>