PCI: fix bogus "'device' may be used uninitialized" warning in pci_slot

I get warnings about 'device' possibly being used uninitialised.  While
I can deduce this is not true, it seems that GCC can't.  This patch
changes `check_slot' to return device on success and -1 on error, which
shuts GCC up.
Acked-by: NAlex Chiang <achiang@hp.com>
Signed-off-by: NMatthew Wilcox <willy@linux.intel.com>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>

drivers/acpi/pci_slot.c

@@ -76,9 +76,9 @@ static struct acpi_pci_driver acpi_pci_slot_driver = {
 };
 
 static int
-check_slot(acpi_handle handle, int *device, unsigned long *sun)
+check_slot(acpi_handle handle, unsigned long *sun)
 {
-	int retval = 0;
+	int device = -1;
 	unsigned long adr, sta;
 	acpi_status status;
 	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
@@ -89,32 +89,27 @@ check_slot(acpi_handle handle, int *device, unsigned long *sun)
 	if (check_sta_before_sun) {
 		/* If SxFy doesn't have _STA, we just assume it's there */
 		status = acpi_evaluate_integer(handle, "_STA", NULL, &sta);
-		if (ACPI_SUCCESS(status) && !(sta & ACPI_STA_DEVICE_PRESENT)) {
-			retval = -1;
+		if (ACPI_SUCCESS(status) && !(sta & ACPI_STA_DEVICE_PRESENT))
 			goto out;
 	}
-	}
 
 	status = acpi_evaluate_integer(handle, "_ADR", NULL, &adr);
 	if (ACPI_FAILURE(status)) {
 		dbg("_ADR returned %d on %s\n", status, (char *)buffer.pointer);
-		retval = -1;
 		goto out;
 	}
 
-	*device = (adr >> 16) & 0xffff;
-
 	/* No _SUN == not a slot == bail */
 	status = acpi_evaluate_integer(handle, "_SUN", NULL, sun);
 	if (ACPI_FAILURE(status)) {
 		dbg("_SUN returned %d on %s\n", status, (char *)buffer.pointer);
-		retval = -1;
 		goto out;
 	}
 
+	device = (adr >> 16) & 0xffff;
 out:
 	kfree(buffer.pointer);
-	return retval;
+	return device;
 }
 
 struct callback_args {
@@ -144,7 +139,8 @@ register_slot(acpi_handle handle, u32 lvl, void *context, void **rv)
 	struct callback_args *parent_context = context;
 	struct pci_bus *pci_bus = parent_context->pci_bus;
 
-	if (check_slot(handle, &device, &sun))
+	device = check_slot(handle, &sun);
+	if (device < 0)
 		return AE_OK;
 
 	slot = kmalloc(sizeof(*slot), GFP_KERNEL);