CONFIG_ARCH_HAS_RNGA is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_ARCH_HAS_RNGA (not configurable)

configname: CONFIG_ARCH_HAS_RNGA

Linux Kernel Configuration
└─>ARCH_HAS_RNGA
In linux kernel since version 2.6.31 (release Date: 2009-09-09)  
depends
CONFIG_ARCH_MXC

is depended by
CONFIG_ARCH_MX31