Tegra pre-silicon platforms do not have chip revisions. This makes the
revision SoC attribute meaningless on these platforms.

Instead, populate the revision SoC attribute with a combination of the
platform name and the chip revision for silicon platforms, and simply
with the platform name on pre-silicon platforms.
Signed-off-by: Kartik <kkartik@nvidia.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>