dt-bindings: cpufreq: update cpu type and clock name for MT8173 SoC

Update the cpu type of cpu2 and cpu3 since MT8173 used Cortex-a72.

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Seiya Wang <seiya.wang@mediatek.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>