arm: dts: socfpga: agilex: Add freeze controller node

The freeze controller is required for FPGA partial reconfig.
This node is disable on default.
Enable this node via u-boot fdt command when needed.

Signed-off-by: Yau Wai Gan <yau.wai.gan@intel.com>
Signed-off-by: Dinesh Maniyam <dinesh.maniyam@intel.com>
Reviewed-by: Tien Fong Chee <tien.fong.chee@intel.com>