Clock support for rk3066,rk3188 and rk3288

This series adds a clock driver infrastructure for Rockchip SoCs in general and clock-definitions for the RK3188 and RK3288 in particular.

The previous attempt to define parts separately in the devicetree did not really fit with the clock structure, which became apparent with more knowledge about the clock tree.

The whole structure should support Rockchip SoCs at least down to the RK28xx (ARM9) which all share a very similar setup of their clock controllers in PLL, divider and gate handling as well as the included softreset parts.

A big change is the move from declaring all mux/dividers/gates individually to declaring them as composite clock branches, making the code better readable and making it possible to keep clocks together in a more natural order.

The changes under drivers/clk apply cleanly to clk-next but the changes in arm/boot/dts require patches from arm-soc, so in the unlikely case of this making it in before the merge window the dts patches should go through arm-soc (or should do so anyway, as they do not directly depend on the drivers/clk changes)