soc/tegra: fuse: Restrict legacy code to 32-bit ARM

For backwards-compatibility with old device trees, if no APBMISC node
exists this driver hard-codes the I/O memory region. All 64-bit ARM
device tree files are recent enough that they can be required to have
this node, and therefore the legacy code path is not required.

Based on work done by Paul Walmsley <pwalmsley@nvidia.com>.

Cc: Paul Walmsley <pwalmsley@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>