default or selected kernelversion does not have config value CONFIG_ATH9K_RATE_CONTROL.
Result is shown for kernelversion 6.2.5

Atheros ath9k rate control


Linux Kernel Configuration
└─>Device Drivers
└─>Network device support
└─>Wireless LAN
└─>Atheros Wireless Cards
└─>Atheros ath9k rate control
In linux kernel since version 2.6.37 (release Date: 2011-01-04)  
Say Y, if you want to use the ath9k specific rate control
module instead of minstrel_ht.