clk: rockchip: rk3036: fix the div offset for emac clock

Due to reference to old version TRM, there are incorrect emac clock node.
The SEL_21_9 is used for the parent div, the SEL_21_4 is used for the
child div.

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