soc/tegra: Register SoC device

Move this code from arch/arm/mach-tegra and make it common among 32-bit
and 64-bit Tegra SoCs. This is slightly complicated by the fact that on
32-bit Tegra, the SoC device is used as the parent for all devices that
are instantiated from device tree.

Signed-off-by: Thierry Reding <treding@nvidia.com>

include/soc/tegra/fuse.h

@@ -65,6 +65,8 @@ int tegra_fuse_readl(unsigned long offset, u32 *value);
 
 extern struct tegra_sku_info tegra_sku_info;
 
+struct device *tegra_soc_device_register(void);
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* __SOC_TEGRA_FUSE_H__ */