IPC: store mapped buffer info in session context

So that it doesn't have to scan over the request buffer again on reply. This also allow us to store additional info like memory mapping

src/core/hle/kernel/server_session.h

@@ -8,6 +8,7 @@
 #include <string>
 #include "common/assert.h"
 #include "common/common_types.h"
+#include "core/hle/kernel/ipc.h"
 #include "core/hle/kernel/object.h"
 #include "core/hle/kernel/wait_object.h"
 #include "core/hle/result.h"
@@ -83,6 +84,9 @@ public:
     /// TODO(Subv): Find a better name for this.
     SharedPtr<Thread> currently_handling;
 
+    /// A temporary list holding mapped buffer info from IPC request, used for during IPC reply
+    std::vector<MappedBufferContext> mapped_buffer_context;
+
 private:
     explicit ServerSession(KernelSystem& kernel);
     ~ServerSession() override;