PCI: fix aer resume sanity check

What we have to check here before calling is err_handler->resume, not
->slot_reset.  Looks like a copy & paste error from report_slot_reset.

Acked-by: Yanmin Zhang <yanmin.zhang@intel.com>
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>