swresample/rematrix: fix typo in clean_layout()

av_channel_layout_index_from_channel() takes an AVChannel value, not a mask.
Signed-off-by: James Almer <jamrial@gmail.com>

libswresample/rematrix.c

@@ -114,7 +114,7 @@ static int clean_layout(AVChannelLayout *out, const AVChannelLayout *in, void *s
 {
     int ret = 0;
 
-    if(av_channel_layout_index_from_channel(in, AV_CH_FRONT_CENTER) < 0 && in->nb_channels == 1) {
+    if (av_channel_layout_index_from_channel(in, AV_CHAN_FRONT_CENTER) < 0 && in->nb_channels == 1) {
         char buf[128];
         av_channel_layout_describe(in, buf, sizeof(buf));
         av_log(s, AV_LOG_VERBOSE, "Treating %s as mono\n", buf);