[PATCH] softmac: use list_for_each_entry

Cleanup using list_for_each_entry.

Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Joe Jezak <josejx@gentoo.org>
Cc: Daniel Drake <dsd@gentoo.org>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>