CONFIG_ARCH_R8A7745 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

RZ/G1E (R8A77450)

configname: CONFIG_ARCH_R8A7745

Linux Kernel Configuration
└─>Renesas ARM SoCs
└─>RZ/G1E (R8A77450)
In linux kernel since version 3.10 (release Date: 2013-06-30)