lime-system: wireless: add option distance_use_auto_if_available

[a-gave]

Closes #932

Introduce the wifi option distance_use_auto_if_available default=true to enforce the value "auto" as distance for radio drivers that supports it like kmod-ath9k when compiled with CONFIG_PACKAGE_ATH_DYNACK=y

Check if driver supports auto setting
To verify the applied coverage run: "iw phy phyX info | grep Coverage"

If the value "auto" is requested for a driver that does not support it, use the lime-defaults value as a safer option than "auto" which could lead to the minimum being applied, potentially compromising long-range outdoor links.

Tested on these devices running lime master and openwrt 24.10.x:

• ubnt_litebeam-m5-xw
• gemtek_wvrtm-127acn
• gemtek_wvrtm-130acn

[ilario]

Thanks!
I consider this as very useful!
Do you know if the auto distance is available on many routers? Only on ath9k?

A doubt on the code:
The function wireless.is_distance_auto_available works trying to set the distance to auto. If a set distance is specified in the options, will it be then applied later or the auto thing will remain? For example, after running lime-config is the active distance the one set in the config files, or the distance remains to auto and the user should reboot for applying the correct distance?