PCI ASPM: cleanup initialization

Clean up ASPM initialization by refactoring some functionality, renaming
functions, and moving things around.

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>