[][MAC80211][mt76][add support to control single sku]

[Description]
Add support to control single sku on/off.

Usage (turn off single sku feature):
echo 1 > sku_disable
wifi down
wifi up

[Release-log]
N/A

Change-Id: I708c89a25729bc6ec77637b09c6e53119346d24a
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/6145186
1 file changed