ARM: tegra: Enable PCIe controller on Cardhu

Root port 2 is routed to the bottom connector on Cardhu and is used by
the development dock to provide gigabit ethernet and USB functionality.

Signed-off-by: Jay Agarwal <jagarwal@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>