soc/tegra: pmc: Implement acquire/release for resets

By implementing the acquire/release protocol, the resets can be shared
with other drivers that also adhere to this protocol. This will be used
for example by the SOR driver to put hardware into a known good state,
irrespective of whether or not the power domain can be reset.

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