arm64: dts: renesas: r8a779f0: Add CPU core clocks

Describe the clocks for the eight Cortex-A55 CPU cores.
CA55 Sub-System 0 (first 2 clusters / CPU cores 0-3) is clocked by Z0φ.
CA55 Sub-System 1 (last 2 clusters / CPU cores 4-7) is clocked by Z1φ.

For now no operating points are defined.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://lore.kernel.org/r/c502087f9affa86dd665def0d990d277a51cc75c.1654701480.git.geert+renesas@glider.be