[PATCH] softmac: update deauth handler to quiet warning

Recently the deauth packet handler was updated to use a deauth packet
struct (identical to the auth packet struct) and this now gives a
warning. This patch updates the code to properly use a deauth struct and
deauth variable.

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