system-arm: Initialize ICC_SRE_EL3 register

Fast model CPU will throw exceptions if ICC_SRE_EL3 is not initialized
before accessing other interrupt controller system registers.

Change-Id: I638f77aa7a3a4ad92abf2554d039c37601fbd44f
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/19649
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

system-arm: Add aarch64 bootloader support for GICv3

Change-Id: If75262709868cc59d320f60273a32397339f1dd5
Signed-off-by: Jairo Balart <jairo.balart@metempsy.com>
Reviewed-on: https://gem5-review.googlesource.com/c/13435
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

system-arm: change system/arm/aarch64_bootloader/boot.S copyright

The aarch64 boot loader was distributed using a BSD license that was
using non-standard formatting. Updated the license to match gem5's
canonical license format and removed the separete LICENSE.txt file.

Change-Id: I660b73ca5ddd922763a2b72051c73d539248ebcf
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/5728
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>

arm: Bootloader fix for v8 over 16 cores

Previous code used a smaller 4 bit mask to test the MPIDR-EL1 register.
The bitmask was extended to support greater than 16 cores.

arm: Add support for ARMv8 (AArch64 & AArch32)

Note: AArch64 and AArch32 interworking is not supported. If you use an AArch64
kernel you are restricted to AArch64 user-mode binaries. This will be addressed
in a later patch.

Note: Virtualization is only supported in AArch32 mode. This will also be fixed
in a later patch.

Contributors:
Giacomo Gabrielli (TrustZone, LPAE, system-level AArch64, AArch64 NEON, validation)
Thomas Grocutt (AArch32 Virtualization, AArch64 FP, validation)
Mbou Eyole (AArch64 NEON, validation)
Ali Saidi (AArch64 Linux support, code integration, validation)
Edmund Grimley-Evans (AArch64 FP)
William Wang (AArch64 Linux support)
Rene De Jong (AArch64 Linux support, performance opt.)
Matt Horsnell (AArch64 MP, validation)
Matt Evans (device models, code integration, validation)
Chris Adeniyi-Jones (AArch64 syscall-emulation)
Prakash Ramrakhyani (validation)
Dam Sunwoo (validation)
Chander Sudanthi (validation)
Stephan Diestelhorst (validation)
Andreas Hansson (code integration, performance opt.)
Eric Van Hensbergen (performance opt.)
Gabe Black