Kernel: Don't use references or pointers to physical addresses

Now the ACPI & PCI code is more safer, because we don't use raw pointers
or references to objects or data that are located in the physical
address space, so an accidental dereference cannot happen easily.
Instead, we use the PhysicalAddress class to represent those addresses.

Kernel/ACPI/ACPIParser.h

@@ -41,7 +41,7 @@ public:
 
     static bool is_initialized();
     static void initialize_limited();
-    virtual ACPI_RAW::SDTHeader* find_table(const char* sig);
+    virtual PhysicalAddress find_table(const char* sig);
 
     virtual void do_acpi_reboot();
     virtual void do_acpi_shutdown();