lavfi/gradfun: support YUV440P

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavfilter/vf_gradfun.c

@@ -170,6 +170,7 @@ static int query_formats(AVFilterContext *ctx)
         AV_PIX_FMT_GRAY8,              AV_PIX_FMT_NV12,
         AV_PIX_FMT_NV21,               AV_PIX_FMT_YUV444P,
         AV_PIX_FMT_YUV422P,            AV_PIX_FMT_YUV411P,
+        AV_PIX_FMT_YUV440P,
         AV_PIX_FMT_NONE
     };