soc/tegra: fuse: Add stub for tegra_sku_info

Drivers that use tegra_sku_info and have COMPILE_TEST are failing to be
build due to the missing stub for tegra_sku_info.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/20201104164923.21238-4-digetx@gmail.comSigned-off-by: Krzysztof Kozlowski <krzk@kernel.org>

include/soc/tegra/fuse.h

@@ -56,7 +56,11 @@ u32 tegra_read_straps(void);
 u32 tegra_read_ram_code(void);
 int tegra_fuse_readl(unsigned long offset, u32 *value);
 
+#ifdef CONFIG_ARCH_TEGRA
 extern struct tegra_sku_info tegra_sku_info;
+#else
+static struct tegra_sku_info tegra_sku_info __maybe_unused;
+#endif
 
 struct device *tegra_soc_device_register(void);