e100: Handle the return values from pci_* functions

This is to resolve warnings during compile time.
Signed-off-by: NJesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: NJohn Ronciak <john.ronciak@intel.com>
Signed-off-by: NJeff Garzik <jgarzik@pobox.com>