avcodec/internal: Use do {} while() for ff_tlog()

Avoids problems when used without braces
Found-by: Clément Bœsch <u@pkh.me>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/internal.h

@@ -57,7 +57,7 @@
 #ifdef TRACE
 #   define ff_tlog(ctx, ...) av_log(ctx, AV_LOG_TRACE, __VA_ARGS__)
 #else
-#   define ff_tlog(ctx, ...) while(0) {}
+#   define ff_tlog(ctx, ...) do {} while(0)
 #endif