aarch64: Porting GIC source files from Firecracker

This commit adds ported code of Generic Interrupt Controller (GIC)
software implementation for AArch64, including both GICv2 and
GICv3 devices. These GIC devices are actually emulated by the
host kernel through KVM and will be used in the guest VM as the
interrupt controller for AArch64.

Signed-off-by: Henry Wang <Henry.Wang@arm.com>

arch/src/aarch64/mod.rs

@@ -1,6 +1,11 @@
 // Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 
+/// Module for the global interrupt controller configuration.
+pub mod gic;
+mod gicv2;
+mod gicv3;
+/// Layout for this aarch64 system.
 pub mod layout;
 
 use crate::RegionType;