PCI ASPM: remove redundant list check

Remove the following check in __pcie_aspm_config_link() because it
nerver be true.

Acked-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>