soc/tegra: Make ARCH_TEGRA_SOC_FOO defaults for NVIDIA Tegra

soc/tegra: Make ARCH_TEGRA_SOC_FOO defaults for NVIDIA Tegra

By convention, only one globally selectable ARCH_PLATFORM is expected
for given SoC platform, defined in arch/arm64/Kconfig.platforms or
arch/arm/mach-*/Kconfig, because we target a single multi-platform
kernel image.

Platforms wanting different granularity, e.g. due to size constraints on
their devices, should be sure that globally only one ARCH_PLATFORM is
selected in defconfig.  Change Tegra per-SoC Kconfig entries to default
to ARCH_TEGRA allowing removal of these per-SoC parts from defconfigs.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Reviewed-by: Linus Walleij <linusw@kernel.org>
[treding@nvidia.com: Fix ARCH_PLATFORM typo, correct spelling]
Signed-off-by: Thierry Reding <treding@nvidia.com>