iwlwifi: mvm: refactor iwl_mvm_query_wakeup_reasons()

Refactor the iwl_mvm_query_wakeup_reasons() function to split the part
that gets the firmware status from the part that sets up the WoWLAN
status.  This will allow netdetect to reuse the code.

Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>