Fix off by one length calciulation.

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@1781 c046a42c-6fe2-441c-8c8c-71466251a162

hw/usb.c

@@ -183,7 +183,7 @@ int set_usb_string(uint8_t *buf, const char *str)
 
     q = buf;
     len = strlen(str);
-    *q++ = 2 * len + 1;
+    *q++ = 2 * len + 2;
     *q++ = 3;
     for(i = 0; i < len; i++) {
         *q++ = str[i];