USB: serial: pl2303: add device id for ztek device

This adds a new device id to the pl2303 driver for the ZTEK device.

Reported-by: Mike Chu <Mike-Chu@prolific.com.tw>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
diff --git a/drivers/usb/serial/pl2303.h b/drivers/usb/serial/pl2303.h
index 42bc082..71fd9da 100644
--- a/drivers/usb/serial/pl2303.h
+++ b/drivers/usb/serial/pl2303.h
@@ -22,6 +22,7 @@
 #define PL2303_PRODUCT_ID_GPRS		0x0609
 #define PL2303_PRODUCT_ID_HCR331	0x331a
 #define PL2303_PRODUCT_ID_MOTOROLA	0x0307
+#define PL2303_PRODUCT_ID_ZTEK		0xe1f1
 
 #define ATEN_VENDOR_ID		0x0557
 #define ATEN_VENDOR_ID2		0x0547