ACPI: remove unnecessary argument checking

acpi_add_single_object() is static, and all callers supply a valid "child"
argument, so we don't need to check it.  This patch also remove some
unnecessary initializations.
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/scan.c

@@ -1222,14 +1222,10 @@ acpi_add_single_object(struct acpi_device **child,
 		       struct acpi_device *parent, acpi_handle handle, int type,
 			struct acpi_bus_ops *ops)
 {
-	int result = 0;
-	struct acpi_device *device = NULL;
+	int result;
+	struct acpi_device *device;
 	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
 
-
-	if (!child)
-		return -EINVAL;
-
 	device = kzalloc(sizeof(struct acpi_device), GFP_KERNEL);
 	if (!device) {
 		printk(KERN_ERR PREFIX "Memory allocation error\n");