iwlwifi: mvm: query firmware for non-QoS seqno

Instead of keeping track of the non-QoS seqno for each station,
query the firmware when suspending, that's more efficient. As
this can fail, move the station ID mangling later in the code.

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