mac80211: Fix low bit rate in IBSS

mac80211: Fix low bit rate in IBSS

This patch fixes regression in iwlwifi IBSS rate scaling caused by patch:

    commit 6bc37c06bc424bcf3f944e6a79e2d5bb537e02ed
    Author: Vladimir Koutny <vlado@work.ksp.sk>
    Date:   Fri Jun 13 16:50:44 2008 +0200

        mac80211: eliminate IBSS warning in rate_lowest_index()

An IBSS station is added in prepare_for_handlers where the rate scaling was
initialized only with single rate matching the received packet.
The correct rate scale information should be updated only in
ieee80211_rx_bss_info function where beacon is parsed. Because
of coding error the rate info was left untouched.
If a beacon has triggered the connection the rate remined 1Mbps.
This patch fixes this coding error

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Cc: Vladimir Koutny <vlado@work.ksp.sk>
Signed-off-by: John W. Linville <linville@tuxdriver.com>