PCI: qcom-ep: Add support for Link down notification

PCI: qcom-ep: Add support for Link down notification

Add support to pass Link down notification to Endpoint function driver so
that the LINK_DOWN event can be processed by the function.

Link: https://lore.kernel.org/r/20230602114756.36586-7-manivannan.sadhasivam@linaro.org
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kishon Vijay Abraham I <kishon@kernel.org>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>