PCI: Add standard PCIe Capability Link ASPM field names
Add standard #defines for ASPM fields in PCI Express Link Capability and
Link Control registers.
Previously we used PCIE_LINK_STATE_L0S and PCIE_LINK_STATE_L1 directly, but
these are defined for the Linux ASPM interfaces, e.g.,
pci_disable_link_state(), and only coincidentally match the actual register
bits. PCIE_LINK_STATE_CLKPM, also part of that interface, does not match
the register bit.