ARM: tegra: Set up L2 cache using Trusted Foundations firmware

On Tegra30 L2 cache should be initialized using firmware call if CPU
is running in insecure mode. Set up the required outer-cache write_sec()
callback early during boot using the firmware API, it is always a NO-OP
on T114+ and is NO-OP on T20/30 if Trusted Foundations firmware node
isn't present in device-tree.

Tested-by: Robert Yang <decatf@gmail.com>
Tested-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>