Use const where appropriate.

Spotted by Reimar.

libavcodec/libvo-aacenc.c

@@ -122,7 +122,7 @@ AVCodec ff_libvo_aacenc_encoder = {
     aac_encode_frame,
     aac_encode_close,
     NULL,
-    .sample_fmts = (enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE},
+    .sample_fmts = (const enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE},
     .long_name = NULL_IF_CONFIG_SMALL("VisualOn libvo-aacenc AAC"),
 };
 

libavcodec/libvo-amrwbenc.c

@@ -120,7 +120,7 @@ AVCodec ff_libvo_amrwbenc_encoder = {
     amr_wb_encode_frame,
     amr_wb_encode_close,
     NULL,
-    .sample_fmts = (enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE},
+    .sample_fmts = (const enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE},
     .long_name = NULL_IF_CONFIG_SMALL("VisualOn libvo-amrwbenc Adaptive Multi-Rate "
                                       "(AMR) Wide-Band"),
 };