mac80211: Set basic rates while joining ibss network

This patch adds support to nl80211 and mac80211 to set basic rates when
joining/creating ibss network.

Original patch was posted by Johannes Berg on the linux-wireless posting list.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Teemu Paasikivi <ext-teemu.3.paasikivi@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>