[PATCH] mac80211: fix vlan bug

VLAN interfaces have yet another bug: they aren't accounted
for properly in the receive path in prepare_for_handlers().
I noticed this by code inspection, but it would be easy for
the compiler to catch such things if we'd just use the proper
enum where appropriate.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>