iwlwifi: mvm: BT Coex - use data from firmware

The data in MailBox comes direclty from the BT core.
We should use the data processed by the WiFi fw that is
appended to the MailBox in the BT Coex notification.
Also decide on whether the Coex type based on the input
from the the firmware and not hard coded.

Also fix the SMPS SISO threshold to 2 (it was 3).

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>