wifi: mt76: mt7996: fix invalid interface combinations

wifi: mt76: mt7996: fix invalid interface combinations

Setting beacon_int_min_gcd and NL80211_IFTYPE_ADHOC in the same interface
combination is invalid, which will trigger the following warning trace
and get error returned from wiphy_register().

[   10.080325] Call trace:
[   10.082761]  wiphy_register+0xc4/0x76c [cfg80211]
[   10.087465]  ieee80211_register_hw+0x800/0xac4 [mac80211]
[   10.092868]  mt76_register_device+0x16c/0x2c0 [mt76]
[   10.097829]  mt7996_register_device+0x740/0x844 [mt7996e]

Fix this by removing unused adhoc iftype.

Fixes: 948f65249868 ("wifi: mt76: mt7996: advertize beacon_int_min_gcd")
Reported-by: Frank Wunderlich <frank-w@public-files.de>
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Tested-By: Frank Wunderlich <frank-w@public-files.de>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://patch.msgid.link/20241007135133.5336-1-shayne.chen@mediatek.com