ACPI: Cleanup sparse warning on acpi_os_initialize1()

This patch cleans up the following sparse warning:

# make C=2 drivers/acpi/osl.o
...
drivers/acpi/osl.c:1775:20: warning: symbol 'acpi_os_initialize1' was not declared. Should it be static?
...
  CC      drivers/acpi/osl.o

Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 6ab2c35..605718f 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -52,6 +52,7 @@
 #include <acpi/acpi.h>
 #include <acpi/acpi_bus.h>
 #include <acpi/processor.h>
+#include "internal.h"
 
 #define _COMPONENT		ACPI_OS_SERVICES
 ACPI_MODULE_NAME("osl");