clk: mvebu: Use of_get_cpu_hwid() to read CPU ID

Use of_get_cpu_hwid() rather than the open coded reading of the CPU
nodes "reg" property. The existing code is in fact wrong as the "reg"
address cells size is 2 cells for arm64. The existing code happens to
work because the DTS files are wrong as well.

Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230327-mvebu-clk-fixes-v2-2-8333729ee45d@kernel.org


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