PCI: aardvark: Move to MSI handling using generic MSI support

The MSI support introduced with the initial Aardvark driver was based
on the msi_controller structure and the of_pci_msi_chip_add() /
of_pci_find_msi_chip_by_node() API, which are being deprecated in
favor of the generic MSI support.

Update the Aardvark driver to use the generic MSI support.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>