CONFIG_XTENSA_PLATFORM_XTFPGA is not available for thedefaultarchitecture x86.
Result is shown for architecture xtensa

XTFPGA

configname: CONFIG_XTENSA_PLATFORM_XTFPGA

Xtensa System Type
└─>XTFPGA
In linux kernel since version 3.1 (release Date: 2011-10-24)  
XTFPGA is the name of Tensilica board family (LX60, LX110, LX200, ML605).
This hardware is capable of running a full Linux distribution.