default or selected kernelversion does not have config value CONFIG_CLK_RCAR_GEN2.
Result is shown for kernelversion 6.9.9

R-Car Gen2 legacy clock support

modulename: clk-rcar-gen2.ko

configname: CONFIG_CLK_RCAR_GEN2

Linux Kernel Configuration
└─>Device Drivers
└─>Common Clock Framework
└─>R-Car Gen2 legacy clock support
In linux kernel since version 3.10 (release Date: 2013-06-30)  
source code:
drivers/clk/renesas/clk-rcar-gen2.c