x86_nano: Cleanup platform

Author: fwsGonzo

src/platform/x86_nano/platform.cpp

@@ -1,19 +1,10 @@
 #include <os>
 #include "../x86_pc/acpi.hpp"
-#include "../x86_pc/pit.hpp"
-#include "../x86_pc/apic.hpp"
-#include "../x86_pc/apic_timer.hpp"
-#include "../x86_pc/ioapic.hpp"
 #include "../x86_pc/idt.hpp"
 
-using namespace x86;
-using namespace std::chrono;
-
-extern "C" uint16_t _cpu_sampling_freq_divider_;
-
 void __arch_poweroff()
 {
-  ACPI::shutdown();
+  x86::ACPI::shutdown();
   __builtin_unreachable();
 }