hw/pci/pcie_aer.c: fix buffer overruns on invalid state load

4) CVE-2013-4529
hw/pci/pcie_aer.c    pcie aer log can overrun the buffer if log_num is
                     too large

There are two issues in this file:
1. log_max from remote can be larger than on local
then buffer will overrun with data coming from state file.
2. log_num can be larger then we get data corruption
again with an overflow but not adversary controlled.

Fix both issues.

Reported-by: Anthony Liguori <anthony@codemonkey.ws>
Reported-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
