Kernel: Add per platform Processor.h headers

The platform independent Processor.h file includes the shared processor
code and includes the specific platform header file.

All references to the Arch/x86/Processor.h file have been replaced with
a reference to Arch/Processor.h.

Kernel/Arch/aarch64/Processor.h

@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 2018-2021, James Mintram <me@jamesrm.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Array.h>
+#include <AK/Concepts.h>
+#include <AK/Function.h>
+#include <AK/Types.h>
+
+namespace Kernel {
+
+class Thread;
+
+//FIXME This needs to go behind some sort of platform abstraction
+//      it is used between Thread and Processor.
+struct [[gnu::aligned(16)]] FPUState
+{
+    u8 buffer[512];
+};
+
+class Processor {
+public:
+    void set_specific(ProcessorSpecificDataID /*specific_id*/, void* /*ptr*/) { }
+    template<typename T>
+    T* get_specific() { return 0; }
+
+    ALWAYS_INLINE static void pause() { }
+    ALWAYS_INLINE static void wait_check() { }
+
+    ALWAYS_INLINE static bool is_initialized()
+    {
+        return false;
+    }
+
+    ALWAYS_INLINE static u32 current_id()
+    {
+        return 0;
+    }
+
+    ALWAYS_INLINE static Thread* current_thread()
+    {
+        return 0;
+    }
+
+    ALWAYS_INLINE static FlatPtr current_in_irq()
+    {
+        return 0;
+    }
+
+    ALWAYS_INLINE static void enter_critical() { }
+    ALWAYS_INLINE static void leave_critical() { }
+    ALWAYS_INLINE static u32 in_critical()
+    {
+        return 0;
+    }
+
+    ALWAYS_INLINE static Processor& current() { return *((Processor*)0); }
+
+    static void deferred_call_queue(Function<void()> /* callback */) { }
+};
+
+}