avfilter/asrc_anoisesrc: change color variable to int

Or it'll cause invalid color and s->filter is NULL.
Please reproduce it with below command on big endian system:
$ ./ffmpeg -f lavfi -i "anoisesrc=d=60:c=1:r=48000" -f s16le -c:a pcm_s16le  -f
null  -
Segmentation fault (core dumped)
Signed-off-by: Limin Wang <lance.lmwang@gmail.com>
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavfilter/asrc_anoisesrc.c

@@ -30,7 +30,7 @@ typedef struct ANoiseSrcContext {
     int sample_rate;
     double amplitude;
     int64_t duration;
-    int64_t color;
+    int color;
     int64_t seed;
     int nb_samples;