arm64: dts: rockchip: Move L3 cache outside CPUs in RK3588(S) SoC dtsi

Move the "l3_cache" node outside the "cpus" node in the base dtsi file for
Rockchip RK3588(S) SoCs.  The A55 and A76 CPU cores in these SoCs belong to
the ARM DynamIQ IP core lineup, which places the L3 cache outside the CPUs
and into the DynamIQ Shared Unit (DSU). [1]  Thus, moving the L3 cache DT
node one level higher in the DT improves the way the physical topology of
the RK3588(S) SoCs is represented in the SoC dtsi files.

While there, add a comment that explains it briefly, to save curious readers
from the need to reference the repository log for a clarification.

[1] ARM DynamIQ Shared Unit revision r4p0 TRM, version 0400-02

Fixes: c9211fa2 ("arm64: dts: rockchip: Add base DT for rk3588 SoC")
Helped-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Dragan Simic <dsimic@manjaro.org>
Link: https://lore.kernel.org/r/84264d0713fb51ae2b9b731e28fc14681beea853.1727345965.git.dsimic@manjaro.org


Signed-off-by: Heiko Stuebner <heiko@sntech.de>