dt-bindings: zynqmp: Move nvmem binding to different position

Mainline is using different possition that's why sync it up.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

diff --git a/Documentation/devicetree/bindings/nvmem/zynqmp_nvmem.txt b/Documentation/devicetree/bindings/nvmem/xlnx,zynqmp-nvmem.txt
similarity index 100%
rename from Documentation/devicetree/bindings/nvmem/zynqmp_nvmem.txt
rename to Documentation/devicetree/bindings/nvmem/xlnx,zynqmp-nvmem.txt