arm64: dts: xilinx: Remove dtsi for fixed clock

Currently CCF clocks sre used in zynqmp dts. So there is no use of
dtsi for fixed clock. Remove dtsi for fixed clock.

Signed-off-by: Rajan Vaja <rajan.vaja@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>