PCI: tegra: Support per-lane PHYs

The current XUSB pad controller bindings are insufficient to describe
PHY devices attached to USB controllers. New bindings have been created
to overcome these restrictions. As a side-effect each root port now is
assigned a set of PHY devices, one for each lane associated with the
root port. This has the benefit of allowing fine-grained control of the
power management for each lane.

Acked-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>