clk: rockchip: fix rk3368 cpuclk divider offsets

Due to a copy-paste error the the rk3368 cpuclk settings were acessing
rk3288-specific register offsets. This never caused problems till now,
as cpu frequency scaling in't used currently at all.

Reported-by: Xing Zheng <zhengxing@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>