ARM: tegra: support Trusted Foundations by default

Support for Trusted Foundations is light and allows the kernel to run on
a wider range of devices, so enable it by default.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>