arm64: zynqmp: Move clock node to zynqmp-clk-ccf.dtsi

Using clock firmware driver is not the only one option how to configure
clock. In past fixed clocks were also used and that configuration is still
valid that's why move clock firmware node to the same file where zynqmp_clk
references are used.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/48bfd8cf0de4d10b9c4d745218595f28954f70d5.1623684253.git.michal.simek@xilinx.com