ARM: tegra: Guard pin controller code with a Kconfig symbol

ARM: tegra: Guard pin controller code with a Kconfig symbol

Pin controller code is not relevant on all Tegra SoC generations, so
guard it with a Kconfig symbol that can be selected by the generations
that need it.

This is in preparation for unifying Tegra186 code with the code used on
older generations.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>