wl1271: 11n Support, functionality and configuration ability

Add 11n ability in scan, connection and using MCS rates.
The configuration is temporary due to the code incomplete and
still in testing process. That plans to be remove in the future.

Signed-off-by: Shahar Levi <shahar_levi@ti.com>
Reviewed-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>