arm64: zynqmp: Add support for zynqmp fpga manager

Add support for zynqmp fpga manager.

Signed-off-by: Nava kishore Manne <nava.manne@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
[m.tretter@pengutronix.de: moved to subnode of firmware]
Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>