usb: fix uninitialized variable warning in keyspan_pda

This fixes the compiler warning.
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/keyspan_pda.c

@@ -408,7 +408,7 @@ static int keyspan_pda_get_modem_info(struct usb_serial *serial,
 			     3, /* get pins */
 			     USB_TYPE_VENDOR|USB_RECIP_INTERFACE|USB_DIR_IN,
 			     0, 0, &data, 1, 2000);
-	if (rc > 0)
+	if (rc >= 0)
 		*value = data;
 	return rc;
 }