PCI/ASPM: Disable L1 before configuring L1 Substates

Per PCIe r6.1, sec 5.5.4, L1 must be disabled while setting ASPM L1 PM
Substates enable bits.  Previously this was enforced by clearing
PCI_EXP_LNKCTL_ASPMC before calling pci_restore_aspm_l1ss_state().

Move the L1 (and L0s, although that doesn't seem required) disable into
pci_restore_aspm_l1ss_state() itself so it's closer to the code that
depends on it.

Link: https://lore.kernel.org/r/20240223213733.GA115410@bhelgaas


Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>