PCI: dwc: Fix dw_pcie_free_msi() if msi_irq is invalid

Check msi_irq variable before calling irq_set_chained_handler() and
irq_set_handler_data(), lest we call those functions for an invalid MSI
IRQ.
Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>

drivers/pci/controller/dwc/pcie-designware-host.c

@@ -298,8 +298,10 @@ int dw_pcie_allocate_domains(struct pcie_port *pp)
 
 void dw_pcie_free_msi(struct pcie_port *pp)
 {
+	if (pp->msi_irq) {
 		irq_set_chained_handler(pp->msi_irq, NULL);
 		irq_set_handler_data(pp->msi_irq, NULL);
+	}
 
 	irq_domain_remove(pp->msi_domain);
 	irq_domain_remove(pp->irq_domain);