CONFIG_SND_SOC_RT5645 (not configurable)

modulename: snd-soc-rt5645.ko

configname: CONFIG_SND_SOC_RT5645

Linux Kernel Configuration
└─>Device Drivers
└─>Sound card support
└─>Advanced Linux Sound Architecture
└─>ALSA for SoC audio support
└─>CODEC drivers
└─>SND_SOC_RT5645
In linux kernel since version 3.10 (release Date: 2013-06-30)  
source code:
sound/soc//codecs/