soc/tegra: pmc: Explicitly initialize all fields

It's not strictly necessary to initialize the fields in struct
tegra_pmc_soc if they are 0/false. However, we already initialize them
explicitly even if unnecessary, so keep doing that for consistency.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>