arm64: dts: zynqmp: Add DT description for si5328 for zcu102/zcu106

Origin DT binding just specify driver but wasn't aligned with DT binding
which came later. Extend description for zcu102 and zcu106 to cover latest
binding.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/82b2b13006307f108ace81c50c213c3857078b57.1611224800.git.michal.simek@xilinx.com