PCI: mvebu: Remove useless MSI enabling code

PCI: mvebu: Remove useless MSI enabling code

Since commit fcc392d501bd2 ("irqchip/armada-370-xp: Use the generic MSI
infrastructure"), the irqchip driver used on Armada 370, XP, 375, 38x, 39x
for the MPIC interrupt controller has been converted to use the generic MSI
infrastructure.

Since this commit, it is no longer registering an msi_controller structure
with the of_pci_msi_chip_add() function. Therefore, having the PCI driver
used on the same platform calling of_pci_find_msi_chip_by_node() is pretty
useless.

The MSI resolution is now done in the generic interrupt resolution code,
since the MSI controller is an irq domain attached to the interrupt
controller node, which is pointed to by the msi-parent DT property in the
PCIe controller node.

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>