[PATCH] softmac: deauthentication implies deassociation

The 802.11 specs state that deauthenticating also implies
disassociating. This patch implements that, which improve the behaviour
of SIOCSIWMLME.

Signed-off-by: Daniel Drake <dsd@gentoo.org>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>