[media] gspca_kinect: fix kinect_read() error path

The error checking code relative to the invocations of kinect_read()
does not return the actual return code of the function just called, it
returns "res" which still contains the value of the last invocation of
a previous kinect_write().

Return the proper value, and while at it also report with -EREMOTEIO the
case of a partial transfer.

Reported-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Antonio Ospite <ospite@studenti.unina.it>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/usb/gspca/kinect.c

@@ -158,7 +158,7 @@ static int send_cmd(struct gspca_dev *gspca_dev, uint16_t cmd, void *cmdbuf,
 	PDEBUG(D_USBO, "Control reply: %d", res);
 	if (actual_len < sizeof(*rhdr)) {
 		pr_err("send_cmd: Input control transfer failed (%d)\n", res);
-		return res;
+		return actual_len < 0 ? actual_len : -EREMOTEIO;
 	}
 	actual_len -= sizeof(*rhdr);