platform/x86: dell-wmi-sysman: fix init_bios_attributes() error handling

Calling release_attributes_data() while holding the "wmi_priv.mutex"
will lead to a dead lock.  The other problem is that if kzalloc() fails
then this should return -ENOMEM but currently it returns success.

Fixes: e8a60aa ("platform/x86: Introduce support for Systems Management Driver over WMI for Dell Systems")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20201103101735.GB1127762@mwanda
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/dell-wmi-sysman/sysman.c

@@ -443,8 +443,10 @@ static int init_bios_attributes(int attr_type, const char *guid)
 
 		/* build attribute */
 		attr_name_kobj = kzalloc(sizeof(*attr_name_kobj), GFP_KERNEL);
-		if (!attr_name_kobj)
+		if (!attr_name_kobj) {
+			retval = -ENOMEM;
 			goto err_attr_init;
+		}
 
 		attr_name_kobj->kset = tmp_set;
 
@@ -486,13 +488,13 @@ static int init_bios_attributes(int attr_type, const char *guid)
 		elements = obj ? obj->package.elements : NULL;
 	}
 
-	goto out;
+	mutex_unlock(&wmi_priv.mutex);
+	return 0;
 
 err_attr_init:
+	mutex_unlock(&wmi_priv.mutex);
 	release_attributes_data();
 	kfree(obj);
-out:
-	mutex_unlock(&wmi_priv.mutex);
 	return retval;
 }