lavfi: make formats API private on next bump.

It is only useful inside filters and we don't allow user filters for
now.

libavfilter/vf_transpose.c

@@ -29,6 +29,7 @@
 #include "libavutil/pixdesc.h"
 #include "libavutil/imgutils.h"
 #include "avfilter.h"
+#include "formats.h"
 
 typedef struct {
     int hsub, vsub;
@@ -83,7 +84,7 @@ static int query_formats(AVFilterContext *ctx)
         PIX_FMT_NONE
     };
 
-    avfilter_set_common_formats(ctx, avfilter_make_format_list(pix_fmts));
+    ff_set_common_formats(ctx, ff_make_format_list(pix_fmts));
     return 0;
 }