tools/target_dec_fuzzer: Fuzz idct_algo value

This should improve coverage
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

tools/target_dec_fuzzer.c

@@ -214,6 +214,8 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
         keyframes                               = bytestream2_get_le64(&gbc);
         ctx->request_channel_layout             = bytestream2_get_le64(&gbc);
 
+        ctx->idct_algo                          = bytestream2_get_byte(&gbc) % 25;
+
         if (extradata_size < size) {
             ctx->extradata = av_mallocz(extradata_size + AV_INPUT_BUFFER_PADDING_SIZE);
             if (ctx->extradata) {