soc/tegra: fuse: Fix build with Tegra194 configuration

If only Tegra194 support is enabled, the tegra30_fuse_read() and
tegra30_fuse_init() function are not declared and cause a build failure.
Add Tegra194 to the preprocessor guard to make sure these functions are
available for Tegra194-only builds as well.

Link: https://lore.kernel.org/r/20200203143114.3967295-1-thierry.reding@gmail.com
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Olof Johansson <olof@lixom.net>