iwlwifi: mvm: BT Coex - fix shared antenna check with new API

The commit below fixed this for the old firmware API only.
Since the new firmware API hasn't been released yet, this
doesn't fix anything on currently existing firmwares.
This completes:

commit afcee962
Author: Eyal Shapira <eyal@wizery.com>
Date:   Mon Feb 9 15:18:17 2015 +0200

    iwlwifi: mvm: fix BT coex shared antenna activity check

type=bugfix
bug=not-tracked
fixes=unknown

Reviewed-by: Eyal Shapira <eyal@wizery.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>