PCI: tegra: Add Tegra210 support

The PCIe host controller found on Tegra X1 is very similar to its
predecessor on Tegra K1. A bug was introduced in the new revision that
is worked around by always enabling the performance counter, otherwise
accesses to configuration space will block for a number of seconds.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Bjorn Helgaas <helgaas@kernel.org>