HID: uhid: use __packed__ for uhid_feature_answer_req

We use __packed__ for all API structures so we can extend them without
breaking alignment rules. We do try to explicitly align the structures,
but to be safe we also use __packed__.
uhid_feature_answer_req is already 64bit aligned so we can add __packed__
without breaking ABI.
Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

include/uapi/linux/uhid.h

@@ -86,7 +86,7 @@ struct uhid_feature_answer_req {
 	__u16 err;
 	__u16 size;
 	__u8 data[UHID_DATA_MAX];
-};
+} __attribute__((__packed__));
 
 struct uhid_event {
 	__u32 type;