PCI/ASPM: Add pci_enable_link_state_locked()

Add pci_enable_link_state_locked() for enabling link states that can be
used in contexts where a pci_bus_sem read lock is already held (e.g. from
pci_walk_bus()).

This helper will be used to fix a couple of potential deadlocks where
the current helper is called with the lock already held, hence the CC
stable tag.

Fixes: f492edb4

 ("PCI: vmd: Add quirk to configure PCIe ASPM and LTR")
Link: https://lore.kernel.org/r/20231128081512.19387-2-johan+linaro@kernel.org
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
[bhelgaas: include helper name in subject, commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: <stable@vger.kernel.org>	# 6.3
Cc: Michael Bottini <michael.a.bottini@linux.intel.com>
Cc: David E. Box <david.e.box@linux.intel.com>