ARM: dts: rockchip: Pass the 'arm,cpu-registers-not-fw-configured' property on rv1108

Since firmware does not initialize  any of the generic timer CPU
registers pass the 'arm,cpu-registers-not-fw-configured' property as
suggested in Documentation/devicetree/bindings/timer/arm,arch_timer.txt.

This also aligns with other Rockchip SoC dtsi files.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>