ACPI: scan: Make acpi_bus_get_device() clear return pointer on error

Set the acpi_device pointer which acpi_bus_get_device() returns-by-
reference to NULL on errors.

We've recently had 2 cases where callers of acpi_bus_get_device()
did not properly error check the return value, so set the returned-
by-reference acpi_device pointer to NULL, because at least some
callers of acpi_bus_get_device() expect that to be done on errors.

[ rjw: This issue was exposed by commit 71da201 ("ACPI: scan:
  Defer enumeration of devices with _DEP lists") which caused it to
  be much more likely to occur on some systems, but the real defect
  had been introduced by an earlier commit. ]

Fixes: 40e7fcb ("ACPI: Add _DEP support to fix battery issue on Asus T100TA")
Fixes: bcfcd40 ("usb: split code locating ACPI companion into port and device")
Reported-by: Pierre-Louis Bossart <[email protected]>
Tested-by: Pierre-Louis Bossart <[email protected]>
Diagnosed-by: Rafael J. Wysocki <[email protected]>
Signed-off-by: Hans de Goede <[email protected]>
Cc: All applicable <[email protected]>
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <[email protected]>

Author: jwrdegoede

drivers/acpi/scan.c

@@ -586,6 +586,8 @@ static int acpi_get_device_data(acpi_handle handle, struct acpi_device **device,
 	if (!device)
 		return -EINVAL;
 
+	*device = NULL;
+
 	status = acpi_get_data_full(handle, acpi_scan_drop_device,
 				    (void **)device, callback);
 	if (ACPI_FAILURE(status) || !*device) {