While grant reference is of type uint32_t, xen-netfront erroneously casts
it to signed short in BUG_ON().
This would lead to the xen domU panic during boot-up or migration when it
is attached with lots of paravirtual devices.
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>