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

EFI Real Time Clock Services

modulename: efirtc.ko

configname: CONFIG_EFI_RTC

Linux Kernel Configuration
└─>Device Drivers
└─>Character devices
└─>EFI Real Time Clock Services
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
source code:
drivers/char/efirtc.c