PCI: cadence: Implement ->msi_map_irq() ops

Implement ->msi_map_irq() ops in order to map physical address to MSI
address and return MSI data.

Link: https://lore.kernel.org/r/20210201195809.7342-12-kishon@ti.com


Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Tom Joseph <tjoseph@cadence.com>