CONFIG_ARCH_R8A7778 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

R-Car M1 (R8A77780)

modulename: setup-r8a7778.ko

configname: CONFIG_ARCH_R8A7778

Linux Kernel Configuration
└─>R-Car M1 (R8A77780)
In linux kernel since version 3.1 (release Date: 2011-10-24)  
source code:
/arch/arm/mach-shmobile/