CONFIG_C6X is not available for thedefaultarchitecture x86.
Result is shown for architecture c6x

CONFIG_C6X (not configurable)

configname: CONFIG_C6X

Linux Kernel Configuration
└─>C6X
In linux kernel since version 3.1 (release Date: 2011-10-24)  

is selected by
CONFIG_BINFMT_ELF_FDPIC