[PATCH] softmac: fix SIOCSIWAP

There are some bugs in the current implementation of the SIOCSIWAP wext,
for example that when you do it twice and it fails, it may still try
another access point for some reason. This patch fixes this by introducing
a new flag that tells the association code that the bssid that is in use
was fixed by the user and shouldn't be deviated from.

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