wifi: rtw89: set WIPHY_FLAG_DISABLE_WEXT before MLO

We will support MLO on 802.11be chip, e.g. RTL8922A, in the future. At that
time being, we will set WIPHY_FLAG_SUPPORTS_MLO according to chip info and
FW features at runtime. But, with WIPHY_FLAG_SUPPORTS_MLO flag, cfg80211
will disable WEXT. In case inconsistent user experience, if 802.11be chip,
we disable WEXT uniformly from now on.

Signed-off-by: Zong-Zhe Yang <kevin_yang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://msgid.link/20240417090050.42607-1-pkshih@realtek.com