PCI: mvebu: Use child_ops API

PCI: mvebu: Use child_ops API

Split struct pci_ops between ops and child_ops. Member ops is used for
accessing PCIe Root Ports via pci-bridge-emul.c driver and child_ops for
accessing real PCIe cards.

There is no need to mix these two struct pci_ops into one as PCI core code
already provides separate callbacks via bridge->ops and bridge->child_ops.

Link: https://lore.kernel.org/r/20220222155030.988-9-pali@kernel.org
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>