clk: rockchip: add a COMPOSITE_DIV_OFFSET clock-type

The div offset of some clocks are different from their mux offset
and the COMPOSITE clock-type require that div and mux offset are
the same, so add a new COMPOSITE_DIV_OFFSET clock-type to handle that.

Signed-off-by: Finley Xiao <finley.xiao@rock-chips.com>
Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>