mac80211: validate extended element ID is present

commit 768c0b19 upstream.

Before attempting to parse an extended element, verify that
the extended element ID is present.

Fixes: 41cbb0f5 ("mac80211: add support for HE")
Reported-by:  <syzbot+59bdff68edce82e393b6@syzkaller.appspotmail.com>
Link: https://lore.kernel.org/r/20211211201023.f30a1b128c07.I5cacc176da94ba316877c6e10fe3ceec8b4dbd7d@changeid


Cc: stable@vger.kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>