A64 Interface: Allow changing processor id.

This commit allows the JIT to be used per guest thread and change it's
core when the thread is migrated.

include/dynarmic/A64/a64.h

@@ -105,6 +105,8 @@ public:
     /// Modify PSTATE
     void SetPstate(std::uint32_t value);
 
+    void ChangeProcessorID(std::size_t new_processor);
+
     /// Clears exclusive state for this core.
     void ClearExclusiveState();