Red Hat: CVE-2022-49416: kernel: wifi: mac80211: fix use-after-free in chanctx code

In the Linux kernel, the following vulnerability has been resolved:

wifi: mac80211: fix use-after-free in chanctx code

In ieee80211_vif_use_reserved_context(), when we have an
old context and the new context's replace_state is set to
IEEE80211_CHANCTX_REPLACE_NONE, we free the old context
in ieee80211_vif_use_reserved_reassign(). Therefore, we
cannot check the old_ctx anymore, so we should set it to
NULL after this point.

However, since the new_ctx replace state is clearly not
IEEE80211_CHANCTX_REPLACES_OTHER, we're not going to do
anything else in this function and can just return to
avoid accessing the freed old_ctx.