[PATCH] softmac: do shared key auth in workqueue

Johann Uhrmann reported a bcm43xx crash and Michael Buesch tracked
it down to a problem with the new shared key auth code (recursive
calls into the driver)

This patch (effectively Michael's patch with a couple of small
modifications) solves the problem by sending the authentication
challenge response frame from a workqueue entry.

I also removed a lone \n from the bcm43xx messages relating to
authentication mode - this small change was previously discussed but
not patched in.

Signed-off-by: Daniel Drake <dsd@gentoo.org>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>