PCI: tegra: Enable the driver on 64-bit ARM

The Tegra PCI host controller driver no longer relies on any of the 32-bit
ARM glue for PCI, so it can be enabled on 64-bit configurations.

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