PCI/MSI: Clarify pci_free_irq_vectors() usage for managed devices

PCI/MSI: Clarify pci_free_irq_vectors() usage for managed devices

Update pci_free_irq_vectors() documentation to clarify that drivers using
pcim_enable_device() must not call pci_free_irq_vectors().

For legacy reasons, pcim_enable_device() switches several normally
un-managed functions into managed mode. Currently, the only function
affected in this way is pcim_setup_msi_release(), which results in
automatic IRQ vector management.

This behavior is dangerous and confusing. Drivers using pcim_enable_device()
should rely on the automatic IRQ vector management and avoid calling
pci_free_irq_vectors() manually.

Suggested-by: Philipp Stanner <phasta@kernel.org>
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
[bhelgaas: squash both updates to pci_free_irq_vectors() documentation]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/1770798299-202288-2-git-send-email-shawn.lin@rock-chips.com
Link: https://patch.msgid.link/1770798299-202288-3-git-send-email-shawn.lin@rock-chips.com