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

Support for RTAS based PowerNV platforms such as BML

configname: CONFIG_PPC_POWERNV_RTAS

Linux Kernel Configuration
└─>Support for RTAS based PowerNV platforms such as BML
In linux kernel since version 3.1 (release Date: 2011-10-24)