pci: pci_mvebu: Split initialization of PCIe ports into 3 phases

pci: pci_mvebu: Split initialization of PCIe ports into 3 phases

In first phase just parse DT properties and fill struct mvebu_pcie. In
second phase setup all PCIe links (without enabling them). And in the last
third phase enable all PCIe links and create UCLASS_PCI device for each
one.

Because parsing of DT is done before UCLASS_PCI is created, we cannot use
DM for this action anymore. So remove .of_to_plat callback and replace it
by ad-hoc function for parsing DT properties and filling struct mvebu_pcie.

Signed-off-by: Pali Rohár <pali@kernel.org>