[RFC 0/5] device wakeup event support v2

This series add device wakeup event detection support. This is the base to
implement runtime device suspend/resume, though we don't support it now.
But David said USB is approaching to this. See this bugzilla
http://bugzilla.kernel.org/show_bug.cgi?id=6892 for detail.

changes v1 -> v2:
1. scan pci bridge for PME. Current implementation is just doing scan if target device is a bridge
2. move device_receive_wakeup_event() call to pci, and provide an API (pci_handle_wakeup_event()) for non-ACPI & non-PCIe platform
3. fixed a lot of coding style issues

Signed-off-by: Shaohua Li <redacted>
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