[PATCH 1/1] PCI/MSI: add NULL check before use of msi_desc

On starting kdump kernel in arm, arm64 and powerpc, chip->irq_mask() is called for each irq_data to mask interrupts. For MSI irqs, pci_msi_mask_irq() is called even when the irq_data doesn't have a link to msi_desc. This results in a NULL pointer dereference. This patch fixes the above error by

[PATCH 1/1] PCI/MSI: add NULL check before use of msi_desc

On starting kdump kernel in arm, arm64 and powerpc, chip->irq_mask() is called for each irq_data to mask interrupts. For MSI irqs, pci_msi_mask_irq() is called even when the irq_data doesn't have a link to msi_desc. This results in a NULL pointer dereference. This patch fixes the above error by