usb-host: Initialize dev->port the obviously safe way

Coverity worries the strcpy() could overrun the destination.  It
can't, because the source always points to usb_host_scan()'s auto
port[], which has the same size.  Use pstrcpy() anyway, to hush the
checker.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

hw/usb/host-linux.c

@@ -1314,7 +1314,7 @@ static int usb_host_open(USBHostDevice *dev, int bus_num,
 
     dev->bus_num = bus_num;
     dev->addr = addr;
-    strcpy(dev->port, port);
+    pstrcpy(dev->port, sizeof(dev->port), port);
     dev->fd = fd;
 
     /* read the device description */