rtl8139: fix Pointer to local outside scope

rtl8139: fix Pointer to local outside scope

Coverity spot:
 Assigning: iov = struct iovec [3]({{buf, 12UL},
                       {(void *)dot1q_buf, 4UL},
                       {buf + 12, size - 12}})
 (address of temporary variable of type struct iovec [3]).
 out_of_scope: Temporary variable of type struct iovec [3] goes out of scope.

Pointer to local outside scope (RETURN_LOCAL)
use_invalid:
 Using iov, which points to an out-of-scope temporary variable of type struct iovec [3].

Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>