iwlwifi enabling IBSS (Ad-Hoc) mode

iwlwifi enabling IBSS (Ad-Hoc) mode

This patch enables ibss mode. It consists of two changes upon entering ibss
mode:
1. Removing the redundant line which clears the driver's station table.
   This line creates a discrepancy between the driver and the FW's station
   table. This prevented the generation of beacons.
2. Assigning a default value to priv's assoc_id. Normally given by an AP in
   STA mode, this field is used as an indication for association. Being 0,
   it prevented normal TX flow.
3. Remove a redundant ADD_STA command that cause uCode error.
4. Delay the set_mode until after the uCode is ready.

Signed-off-by: Assaf Krauss <assaf.krauss@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>