module: zfs: fix unused, remove argsused

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #12844

module/zfs/spa_errlog.c

@@ -252,6 +252,8 @@ spa_get_errlog(spa_t *spa, void *uaddr, size_t *count)
 	mutex_exit(&spa->spa_errlist_lock);
 
 	mutex_exit(&spa->spa_errlog_lock);
+#else
+	(void) spa, (void) uaddr, (void) count;
 #endif
 
 	return (ret);