clk: mvebu: Iterate over possible CPUs instead of DT CPU nodes

Rework iterating over DT CPU nodes to iterate over possible CPUs
instead. There's no need to walk the DT CPU nodes again. Possible CPUs
is equal to the number of CPUs defined in the DT. Using the "reg" value
for an array index is fragile as it assumes "reg" is 0-N which often is
not the case.

Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230327-mvebu-clk-fixes-v2-3-8333729ee45d@kernel.org


Signed-off-by: Stephen Boyd <sboyd@kernel.org>