mac80211: fix WPA with VLAN on AP side with ps-sta again

commit de74a1d9
  "mac80211: fix WPA with VLAN on AP side with ps-sta"
fixed an issue where queued multicast packets would
be sent out encrypted with the key of an other bss.

commit "7cbf9d01"
  "mac80211: fix oops on mesh PS broadcast forwarding"
essentially reverted it, because vif.type cannot be AP_VLAN
due to the check to vif.type in ieee80211_get_buffered_bc before.

As the later commit intended to fix the MESH case, fix it
by checking for IFTYPE_AP instead of IFTYPE_AP_VLAN.

Cc: stable@vger.kernel.org
Fixes: 7cbf9d01

 ("mac80211: fix oops on mesh PS broadcast forwarding")
Signed-off-by: Michael Braun <michael-dev@fami-braun.de>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>