ARM: tegra: move CONFIG_TEGRAnn

<asm/arch-tegra/tegra.h> needs to use CONFIG_TEGRA* to conditionalize
some definitions, since some modules moved between generations. Move
the definition of CONFIG_TEGRAnn to a header that's included earlier,
so that it's set by the time tegra.h needs to use it.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>