ARM: dts: rockchip: Update compatible property for rk322x timer

Property set to '"rockchip,rk3228-timer", "rockchip,rk3288-timer"'
to match devicetree bindings.

Signed-off-by: Alexander Kochetkov <al.kochet@gmail.com>
Suggested-by: Heiko Stübner <heiko@sntech.de>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>