[][MAC80211][WiFi6/7][iw][Add support for 5G U-NII-3 & 4 setting without specifying center]

[Description]
Add support for 5G U-NII-3 setting without specifying center freq
Fix 6G freq typo (6195 --> 6915)

[Release-log]
N/A

Change-Id: If6d025a16ae736b0f9e8da498c332b584844aa15
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/8140432
1 file changed