vmm: raise the (v)CPU limit on kvm/x86_64

Raise the max number of supported (v)CPUs on kvm x86_64 hosts
to 8192 (the max allowed value of CONFIG_NR_CPUS in the Linux kernel).

Other platfroms keep their existing CPU limits pending further
development and testing.

The change has been tested on Intel and AMD hosts.

Signed-off-by: Barret Rhoden <brho@google.com>
Signed-off-by: Neel Natu <neelnatu@google.com>
Signed-off-by: Ofir Weisse <oweisse@google.com>
Signed-off-by: Peter Oskolkov <posk@google.com>

vmm/src/device_manager.rs

@@ -1694,7 +1694,7 @@ impl DeviceManager {
     ) -> DeviceManagerResult<Arc<Mutex<dyn InterruptController>>> {
         let interrupt_controller: Arc<Mutex<gic::Gic>> = Arc::new(Mutex::new(
             gic::Gic::new(
-                self.config.lock().unwrap().cpus.boot_vcpus as u32,
+                self.config.lock().unwrap().cpus.boot_vcpus,
                 Arc::clone(&self.msi_interrupt_manager),
                 self.address_manager.vm.clone(),
             )