This allows readl-only composite clocks by making mux_ops->set_parent and
divider_ops->round_rate/set_rate optional.
Signed-off-by: NHeiko Stuebner <heiko@sntech.de>
Acked-By: NMax Schwarz <max.schwarz@online.de>
Tested-By: NMax Schwarz <max.schwarz@online.de>
Signed-off-by: NMike Turquette <mturquette@linaro.org>