Necessary functionality support for spawning microVMs on aarch64

[dianpopa]

• Implement the equivalent of function arch_memory_regions for aarch64 (i.e a function that returns the valid memory addresses for this architecture). Checkout 3.5 Chapter from the A-72 Cortex processor
  and [crosvm] Memory layout representation for aarch64 #1003
  (https://chromium.googlesource.com/chromiumos/platform/crosvm/+/master/aarch64/src/lib.rs).
• Platform dependent irq assignment for the mmio device manager Implement platform dependent irq assignment for the mmio device manager #1001.
• Merge Fix inconsistency with libc attribute decoration nathansizemore/epoll#8.
• Implement specific aarch64 system configuration (i.e interrupts and registers). See configure_system function. Use the the in-kernel GIC support for the hardware VGIC features (additional kernel config flag required).
• Create the Flatten Device Tree of the vm that should be spawned.
• Implement specific device allocation for aarch64 (i.e mmio device allocation)
  • Is the mmio base address architecture specific?
  • Maybe fix Enforce Memory Limitations While Registering a mmio Device #58?
• Implement kernel loading
• Zero page start for aarch64?
• Kernel cmdline start for aarch64?
• Working aarch64 kernel config

[dianpopa]

Uploaded the necessary images for spawning a aarch64 guest.