usb: Simplify the parameter parsing of the legacy usb serial device

Coverity complains about the current code, so let's get rid of
the now unneeded while loop and simply always emit "unrecognized
serial USB option" for all unsupported options.
Signed-off-by: NThomas Huth <thuth@redhat.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Message-id: 1495177204-16808-1-git-send-email-thuth@redhat.com
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

hw/usb/dev-serial.c

@@ -516,27 +516,16 @@ static USBDevice *usb_serial_init(USBBus *bus, const char *filename)
     char label[32];
     static int index;
 
-    while (*filename && *filename != ':') {
-        const char *p;
-
-        if (strstart(filename, "vendorid=", &p)) {
-            error_report("vendorid is not supported anymore");
-            return NULL;
-        } else if (strstart(filename, "productid=", &p)) {
-            error_report("productid is not supported anymore");
-            return NULL;
-        } else {
+    if (*filename == ':') {
+        filename++;
+    } else if (*filename) {
         error_report("unrecognized serial USB option %s", filename);
         return NULL;
     }
-        while(*filename == ',')
-            filename++;
-    }
     if (!*filename) {
         error_report("character device specification needed");
         return NULL;
     }
-    filename++;
 
     snprintf(label, sizeof(label), "usbserial%d", index++);
     cdrv = qemu_chr_new(label, filename);