default or selected kernelversion does not have config value CONFIG_ATH6K_LEGACY.
Result is shown for kernelversion 6.2.5

Atheros AR6003 support (non mac80211)

modulename: ath6kl.ko


Linux Kernel Configuration
└─>Device Drivers
└─>Staging drivers
└─>MMC/SD/SDIO card support
└─>Wireless LAN
└─>Atheros AR6003 support (non mac80211)
In linux kernel since version 2.6.37 (release Date: 2011-01-04)  
This module adds support for wireless adapters based on Atheros AR6003 chipset running over SDIO. If you choose to build it as a module, it will be called ath6kl. Pls note that AR6002 and AR6001 are not supported by this driver.

source code: