Replace gcc variadic macro extension with C99 version

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/hw/ppc_newworld.c b/hw/ppc_newworld.c
index 760249e..29faa06 100644
--- a/hw/ppc_newworld.c
+++ b/hw/ppc_newworld.c
@@ -44,10 +44,10 @@
 //#define DEBUG_UNIN
 
 #ifdef DEBUG_UNIN
-#define UNIN_DPRINTF(fmt, args...) \
-do { printf("UNIN: " fmt , ##args); } while (0)
+#define UNIN_DPRINTF(fmt, ...)                                  \
+    do { printf("UNIN: " fmt , ## __VA_ARGS__); } while (0)
 #else
-#define UNIN_DPRINTF(fmt, args...)
+#define UNIN_DPRINTF(fmt, ...)
 #endif
 
 /* UniN device */