qdev: Separate USB product description from qdev name

Using the qdev name for the product description makes for inconvenient
qdev names.

Put the product description in new USBDeviceInfo member product_desc.
Make usb_qdev_init() use it.  No user or guest visible change, since
the value is still the same.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/hw/usb-bus.c b/hw/usb-bus.c
index ba1b6e3..8bbc80d 100644
--- a/hw/usb-bus.c
+++ b/hw/usb-bus.c
@@ -43,7 +43,7 @@
     USBDeviceInfo *info = DO_UPCAST(USBDeviceInfo, qdev, base);
     int rc;
 
-    pstrcpy(dev->product_desc, sizeof(dev->product_desc), qdev->info->name);
+    pstrcpy(dev->product_desc, sizeof(dev->product_desc), info->product_desc);
     dev->info = info;
     dev->auto_attach = 1;
     rc = dev->info->init(dev);