devices: remove the migration traits for the Gic struct

Unlike x86_64, the "interrupt_controller" in the device manager
for AArch64 is only a `Gic` object that implements the
`InterruptController` to provide the interrupt delivery service.
This is not the real GIC device so that we do not need to save
its states. Also, we do not need to insert it to the device_tree.

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

devices/src/gic.rs

@@ -8,7 +8,6 @@ use std::sync::Arc;
 use vm_device::interrupt::{
     InterruptIndex, InterruptManager, InterruptSourceGroup, MsiIrqGroupConfig,
 };
-use vm_migration::{Migratable, MigratableError, Pausable, Snapshot, Snapshottable, Transportable};
 
 type Result<T> = result::Result<T, Error>;
 
@@ -63,22 +62,3 @@ impl InterruptController for Gic {
         Ok(())
     }
 }
-
-const GIC_SNAPSHOT_ID: &str = "gic";
-impl Snapshottable for Gic {
-    fn id(&self) -> String {
-        GIC_SNAPSHOT_ID.to_string()
-    }
-
-    fn snapshot(&mut self) -> std::result::Result<Snapshot, MigratableError> {
-        unimplemented!();
-    }
-
-    fn restore(&mut self, _snapshot: Snapshot) -> std::result::Result<(), MigratableError> {
-        unimplemented!();
-    }
-}
-
-impl Pausable for Gic {}
-impl Transportable for Gic {}
-impl Migratable for Gic {}