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

Enable full debugging output in 4965 and 3945 drivers

configname: CONFIG_IWLWIFI_LEGACY_DEBUG

Linux Kernel Configuration
└─>Device Drivers
└─>Network device support
└─>Wireless LAN
└─>Debugging Options
└─>Enable full debugging output in 4965 and 3945 drivers
In linux kernel since version 2.6.39 (release Date: 2011-05-18)  
This option will enable debug tracing output for the iwlwifilegacy
drivers.

This will result in the kernel module being ~100k larger. You can
control which debug output is sent to the kernel log by setting the
value in

/sys/class/net/wlan0/device/debug_level

This entry will only exist if this option is enabled.

To set a value, simply echo an 8-byte hex value to the same file:

% echo 0x43fff > /sys/class/net/wlan0/device/debug_level

You can find the list of debug mask values in:
drivers/net/wireless/iwlwifilegacy/iwl-debug.h

If this is your first time using this driver, you should say Y here
as the debug information can assist others in helping you resolve
any problems you may encounter.