CONFIG_EPAPR_BOOT is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

CONFIG_EPAPR_BOOT (not configurable)

configname: CONFIG_EPAPR_BOOT

Linux Kernel Configuration
└─>EPAPR_BOOT
In linux kernel since version 3 (release Date: 2011-07-21)  
Used to allow a board to specify it wants an ePAPR compliant wrapper.

is depended by
CONFIG_PPC_POWERNV