10687 Service routine cast changes need smatch fixes

@@ -21,10 +21,13 @@
 /*
  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 
+/*
+ * Copyright 2019, Joyent, Inc.
+ */
 
 #include <sys/types.h>
 #include <inet/common.h>
 #include <sys/stropts.h>
 #include <sys/modctl.h>

@@ -660,11 +663,11 @@
                 /*
                  * Bump su_tx_inprocess so that su_mode won't change.
                  */
                 sup->su_tx_inprocess++;
                 mutex_exit(&sup->su_mutex);
-                dld_wsrv(wq);
+                (void) dld_wsrv(wq);
                 mutex_enter(&sup->su_mutex);
                 if (--sup->su_tx_inprocess == 0)
                         cv_signal(&sup->su_cv);
         } else if (sup->su_tx_busy && SOFTMAC_CANPUTNEXT(sup->su_slp->sl_wq)) {
                 /*