clk: zynq: Add clock wizard driver

The Clocking Wizard IP supports clock circuits customized
to your clocking requirements. The wizard support for
dynamically reconfiguring the clocking primitives for
Multiply, Divide, Phase Shift/Offset, or Duty Cycle.

Limited by U-Boot clk uclass without set_phase API, this
patch only provides set_rate to modify the frequency.

Signed-off-by: Zhengxun <zhengxunli.mxic@gmail.com>
Reviewed-by: Sean Anderson <sean.anderson@seco.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>