ACPI: delete dead acpi_disabled setting code

Testing CONFIG_ACPI inside boot.c is a waste of text,
since boot.c is built only when CONFIG_ACPI=y

Signed-off-by: Len Brown <len.brown@intel.com>

arch/x86/kernel/acpi/boot.c

@@ -43,11 +43,7 @@
 
 static int __initdata acpi_force = 0;
 u32 acpi_rsdt_forced;
-#ifdef	CONFIG_ACPI
-int acpi_disabled = 0;
-#else
-int acpi_disabled = 1;
-#endif
+int acpi_disabled;
 EXPORT_SYMBOL(acpi_disabled);
 
 #ifdef	CONFIG_X86_64