fft-test: add a missing #include

stdio.h needed for printf since 7177df90a0

libavcodec/fft-test.c

@@ -37,6 +37,7 @@
 #if HAVE_UNISTD_H
 #include <unistd.h>
 #endif
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>