iscsi-scst: Port to Linux kernel versions >= v4.7

git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@7021 d57e44dd-8a1f-0410-8b47-8ef2f437770f

iscsi-scst/kernel/nthread.c

@@ -727,7 +727,10 @@ restart:
 
 	oldfs = get_fs();
 	set_fs(get_ds());
-	res = sock_recvmsg(conn->sock, msg, read_size,
+	res = sock_recvmsg(conn->sock, msg,
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 7, 0)
+			   read_size,
+#endif
 			   MSG_DONTWAIT | MSG_NOSIGNAL);
 	set_fs(oldfs);