avfilter/vf_nnedi: Fix memleak

Fixes CID1351359
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavfilter/vf_nnedi.c

@@ -1154,7 +1154,7 @@ static av_cold int init(AVFilterContext *ctx)
 
     s->fdsp = avpriv_float_dsp_alloc(0);
     if (!s->fdsp)
-        return AVERROR(ENOMEM);
+        ret = AVERROR(ENOMEM);
 
 fail:
     av_free(bdata);