iwlwifi: mvm: add some missing cleanups in iwl_mvm_mac_add_interface

iwl_mvm_mac_add_interface() didn't clean up beacon filtering
configuration and ctxt allocation in some error cases.

Signed-off-by: Eliad Peller <eliad@wizery.com>
Reviewed-by: Alexander Bondar <alexander.bondar@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>