clk: tegra: Register clocks from root to leaf

Current clock initialization causes intermediate registering of orphan
clocks (i.e. a clock without a parent registered). CCF keeps track of
orphan clocks and any time a new clock is registered, it will loop
through the list of orphan and queries if the parent is now available.
This operation triggers one or more clock operations, which are IPCs
with BPMP-FW. Hence, due to the order in which the clocks appear
currently, this causes > 5000 IPC messages to be sent to BPMP-FW during
clock initialization.

Optimize the clock probing by registering clocks hierarchically from
root clock towards leafs.

Signed-off-by: Timo Alho <talho@nvidia.com>
[jonathanh@nvidia.com: checkpatch fixes]
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>