iwlwifi: use the results from disconnected antenna algorithm

This patch makes usage of the results from disconnected antenna alg to
know how many antennas are connected.

It also synchronizes between the chain noise alg and the W/A that
disables power management during association. All the antennas must be
enables during the chain noise algorithm. Hence, power management is
restored only after the completion of the algorithm.

In the future, we will need to update the AP that we don't support MIMO
if there is only one antenna connected. We also need to update the rate
scaling algorithm.

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>