arm64: dts: allwinner: h6: Add clock to CPU cores

The ARM CPU cores are fed by the CPU clock from the CCU. Add a
reference to the clock for each CPU core, along with the clock
transition latency.

Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: Clément Péron <peron.clem@gmail.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>