When working in ibss mode, we don't configure rate policy per station
(as we use the same link for multiple stations), so currently the
1mb/s rate is being used.

Instead, configure the firmware to use the whole 11b rates by default.
Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>