shellcode: recognize aarch64 as ARM64
shellcode: recognize aarch64 as ARM64

The shellcode works fine on a non-virtualized system:

    $ strace ./shellcode.py -qr

    mmap(NULL, 48, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xffff9f56a000
    mprotect(0xffff9f56a000, 48, PROT_READ|PROT_EXEC) = 0
    execve("/bin//sh", ["/bin//sh"], NULL)  = 0

fishilico/shared,fishilico/shared,fishilico/shared,fishilico/shared,fishilico/shared,fishilico/shared,fishilico/shared