The pcibios_msi_controller() hook was only implemented by ARM, and it sets
pci_bus->msi now, so it doesn't need this hook anymore.
Remove the unused pcibios_msi_controller() hook.
[bhelgaas: changelog, split into separate patch] Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>