Correct post load checks:
1. dev->setup_len == sizeof(dev->data_buf)
    seems fine, no need to fail migration
2. When state is DATA, passing index > len
   will cause memcpy with negative length,
   resulting in heap overflow

First of the issues was reported by dgilbert.

Reported-by: "Dr. David Alan Gilbert" <dgilbert <at> redhat.com>
Signed-off-by: Michael S. Tsirkin <mst <at> redhat.com>
---

changes from v1:
- drop state check
- lightly tested

 hw/usb/bus.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/usb/bus.c b/hw/usb/bus.c
index e48b19f..ff1dfe6 100644
--- a/hw/usb/bus.c
+++ b/hw/usb/bus.c
 <at>  <at>  -51,8 +51,8  <at>  <at>  static int usb_device_post_load(void *opaque, int version_id)
     }
     if (dev->setup_index < 0 ||
         dev->setup_len < 0 ||
-        dev->setup_index >= sizeof(dev->data_buf) ||
-        dev->setup_len >= sizeof(dev->data_buf)) {
+        dev->setup_index > dev->setup_len ||
+        dev->setup_len > sizeof(dev->data_buf)) {
         return -EINVAL;
     }
     return 0;