wifi: mac80211: disable softirqs for queued frame handling

As noticed by syzbot, calling ieee80211_handle_queued_frames()
(and actually handling frames there) requires softirqs to be
disabled, since we call into the RX code. Fix that in the case
of cleaning up frames left over during shutdown.

Fixes: 177c6ae9

 ("wifi: mac80211: handle tasklet frames before stopping")
Reported-by:  <syzbot+1d516edf1e74469ba5d3@syzkaller.appspotmail.com>
Link: https://patch.msgid.link/20240626091559.cd6f08105a6e.I74778610a5ff2cf8680964698131099d2960352a@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>