PCI aer: fix stub return values

The stubs used when advanced error reporting is not enabled
must have same return type as real functions.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Acked-by: Zhang Yanmin <yanmin.zhang@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>