Capture PCIe aspm status
It'd be useful for the system to capture the initial ASPM (active state power monitoring) status of a given PCIe device as on some platforms ASPM can cause trouble and this gives us a way to visualize it by adding information to prtconf. In particular this adds two fields:
- 'pcie-aspm-support' which is set to indicate a combination of l0s and l1
- 'pcie-aspm-state' which is set to one of 'disabled', 'l0s', 'l1', and 'l0s,l1'