PCI/ASPM: Simplify Clock Power Management setting

Update the Link Control Enable Clock Power Management bit the same
way we update the ASPM Control bits, with a single call of
pcie_capability_clear_and_set_word().

No functional change; this just makes both paths use the same style.

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

diff --cc drivers/pci/pcie/aspm.c
Simple merge