iwlwifi: mvm: remove support for adjacent channel compensation

We no longer want to consider the RSSI if the beacon / probe
has been heard on an adjacent channel.
This was based on a firmware capability that is now
unavailable.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>