vmm,devices: Change Gic snapshot and restore path

The snapshot and restore of AArch64 Gic was done in Vm. Now it is moved
to DeviceManager.

The benefit is that the restore can be done while the Gic is created in
DeviceManager.

While the moving of state data from Vm snapshot to DeviceManager
snapshot breaks the compatability of migration from older versions.

Signed-off-by: Michael Zhao <michael.zhao@arm.com>

devices/src/interrupt_controller.rs

@@ -24,8 +24,12 @@ pub enum Error {
     UpdateInterrupt(io::Error),
     /// Failed enabling the interrupt.
     EnableInterrupt(io::Error),
+    #[cfg(target_arch = "aarch64")]
     /// Failed creating GIC device.
     CreateGic(hypervisor::HypervisorVmError),
+    #[cfg(target_arch = "aarch64")]
+    /// Failed restoring GIC device.
+    RestoreGic(hypervisor::arch::aarch64::gic::Error),
 }
 
 type Result<T> = result::Result<T, Error>;