CONFIG_FIT_IMAGE_FDT_XILFPGA is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

Include FDT for Xilfpga


Linux Kernel Configuration
└─>Include FDT for Xilfpga
In linux kernel since version 4.2 (release Date: 2015-08-30)  
Enable this to include the FDT for the MIPSfpga platform
from Imagination Technologies in the FIT kernel image.