CONFIG_ARCH_RCAR_GEN2 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_ARCH_RCAR_GEN2 (not configurable)

modulename: setup-rcar-gen2.ko

and/or

pm-rcar-gen2.ko

configname: CONFIG_ARCH_RCAR_GEN2

Linux Kernel Configuration
└─>ARCH_RCAR_GEN2
In linux kernel since version 3.10 (release Date: 2013-06-30)  
source code:
/arch/arm/mach-shmobile/
selects
CONFIG_PM
CONFIG_PM_GENERIC_DOMAINS
CONFIG_RENESAS_IRQC
CONFIG_SYS_SUPPORTS_SH_CMT

is depended by
CONFIG_ARCH_R8A7790