USB: add a pl2303 device id

As reported by Ken A Scott <kscott9@sent.com>

Cc: Ken A Scott <kscott9@sent.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/serial/pl2303.h b/drivers/usb/serial/pl2303.h
index cff160a..6ac3bbc 100644
--- a/drivers/usb/serial/pl2303.h
+++ b/drivers/usb/serial/pl2303.h
@@ -15,6 +15,7 @@
 #define PL2303_PRODUCT_ID_RSAQ3		0xaaa2
 #define PL2303_PRODUCT_ID_ALDIGA	0x0611
 #define PL2303_PRODUCT_ID_MMX		0x0612
+#define PL2303_PRODUCT_ID_GPRS		0x0609
 
 #define ATEN_VENDOR_ID		0x0557
 #define ATEN_VENDOR_ID2		0x0547