kernel/x86: Make acpi_read & acpi_write private (static).

They aren't used anywhere outside this file anymore, and they
shouldn't be used when X2APIC is enabled, anyway.

headers/private/kernel/arch/x86/apic.h

@@ -111,8 +111,6 @@
 
 bool		apic_available();
 bool		x2apic_available();
-uint32		apic_read(uint32 offset);
-void		apic_write(uint32 offset, uint32 data);
 uint32		apic_local_id();
 uint32		apic_local_version();
 uint32		apic_task_priority();

src/system/kernel/arch/x86/apic.cpp

@@ -39,14 +39,14 @@ x2apic_available()
 }
 
 
-uint32
+static uint32
 apic_read(uint32 offset)
 {
 	return *(volatile uint32 *)((char *)sLocalAPIC + offset);
 }
 
 
-void
+static void
 apic_write(uint32 offset, uint32 data)
 {
 	*(volatile uint32 *)((char *)sLocalAPIC + offset) = data;