UPSTREAM: clk: rockchip: include rk3288 downstream muxes into fractional dividers

UPSTREAM: clk: rockchip: include rk3288 downstream muxes into fractional dividers

During the initial conversion to the newly introduced combined fractional
dividers+muxes the rk3228 clocks were left out, so convert them now.

Signed-off-by: Xing Zheng <zhengxing@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
(cherry picked from git://git.kernel.org/pub/scm/linux/kernel/git/mmind/linux-rockchip.git
v4.8-clk/next commit c73f689eea9f1e1706a600a506ba89f82bd84349)

Change-Id: Iea91d23ec1fa09c4777f7ccdb016514c301f90ec
Signed-off-by: Xing Zheng <zhengxing@rock-chips.com>