iwlwifi: mvm: Don't warn on command failure during restart

When HW restart is requested but not started yet, commands would not
be sent to the FW, and some function calls return an error. Such cases
can trigger unneeded warning messages, e.g., in iwl_mvm_mac_sta_state()
and iwl_mvm_bss_info_changed_station().

Handle a couple of these cases by also checking in the WARN_ON()
condition that HW restart is not requested.

Signed-off-by: Ilan Peer <ilan.peer@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>