soc/tegra: Restrict SoC device registration to Tegra

Commit 8a46828e623c ("soc/tegra: Register SoC device") added an initcall
to register the SoC device on Tegra. However, that code is unrestricted
and will run on all platforms, causing unwanted warnings.

Fix this by first checking that we're running on hardware that supports
the fuses block that we use to provide SoC information.

Fixes: 8a46828e623c ("soc/tegra: Register SoC device")
Reported-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>