HID: fix a potential bug in pointer casting

Don't directly cast list_head * to foo *, this works only when list
is the first member of struct foo, and we should not make the assumption
how members are ordered in the structure.

i.e. struct *f = (struct *f)pos will work if:
	struct foo {
		struct list_head list;
		int i;
	};

but will fail if:
	struct foo {
		int i;
		struct list_head list;
	}
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/usbhid/hid-tmff.c

@@ -137,7 +137,8 @@ static int hid_tmff_play(struct input_dev *dev, void *data, struct ff_effect *ef
 int hid_tmff_init(struct hid_device *hid)
 {
 	struct tmff_device *tmff;
-	struct list_head *pos;
+	struct hid_report *report;
+	struct list_head *report_list;
 	struct hid_input *hidinput = list_entry(hid->inputs.next, struct hid_input, list);
 	struct input_dev *input_dev = hidinput->input;
 	const signed short *ff_bits = ff_joystick;
@@ -149,8 +150,8 @@ int hid_tmff_init(struct hid_device *hid)
 		return -ENOMEM;
 
 	/* Find the report to use */
-	list_for_each(pos, &hid->report_enum[HID_OUTPUT_REPORT].report_list) {
-		struct hid_report *report = (struct hid_report *)pos;
+	report_list = &hid->report_enum[HID_OUTPUT_REPORT].report_list;
+	list_for_each_entry(report, report_list, list) {
 		int fieldnum;
 
 		for (fieldnum = 0; fieldnum < report->maxfield; ++fieldnum) {