wmi: parse_wdg() should return kernel error codes

The current code returns a mix of acpi_status and kernel error codes.
It should just return kernel error codes.  There are already error paths
in this function which return -ENOMEM and that's what the caller
expects.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>