[media] gspca: konica: add missing endpoint sanity check

Make sure to check the number of endpoints to avoid accessing memory
beyond the endpoint array should a device lack the expected endpoints.

Note that, as far as I can tell, the gspca framework has already made
sure there is at least one endpoint in the current alternate setting so
there should be no risk for a NULL-pointer dereference here.

Fixes: b517af72 ("V4L/DVB: gspca_konica: New gspca subdriver for
konica chipset using cams")

Cc: stable <stable@vger.kernel.org>     # 2.6.37
Cc: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/usb/gspca/konica.c

@@ -184,6 +184,9 @@ static int sd_start(struct gspca_dev *gspca_dev)
 		return -EIO;
 	}
 
+	if (alt->desc.bNumEndpoints < 2)
+		return -ENODEV;
+
 	packet_size = le16_to_cpu(alt->endpoint[0].desc.wMaxPacketSize);
 
 	n = gspca_dev->cam.cam_mode[gspca_dev->curr_mode].priv;