arm64: dts: rockchip: Describe why is HWRNG disabled in RK356x base dtsi

arm64: dts: rockchip: Describe why is HWRNG disabled in RK356x base dtsi

Despite the presence of the hardware random number generator (HWRNG) in the
different Rockchip RK356x SoC variants, it remains disabled for the RK3566
SoC because testing showed [1] that it produces unacceptably low quality of
random data, for some yet unknown reason.  The HWRNG is enabled for the RK3568
SoC, on which the testing showed good quality of the generated random data.

To avoid possible confusion in the future, [2] let's have this described
briefly in the RK356x base SoC dtsi.

[1] https://lore.kernel.org/linux-rockchip/cover.1720969799.git.daniel@makrotopia.org/T/#u
[2] https://lore.kernel.org/linux-rockchip/20241201234613.52322-1-pbrobinson@gmail.com/T/#u

Signed-off-by: Dragan Simic <dsimic@manjaro.org>
Reviewed-by: Diederik de Haas <didi.debian@cknow.org>
Link: https://lore.kernel.org/r/6b272e2f8f916c04b05db50df621659a5a7f29ab.1733149874.git.dsimic@manjaro.org
Signed-off-by: Heiko Stuebner <heiko@sntech.de>