tools/target_dec_fuzzer: Fix build failure from channels API

Regression since 2f8ccca2fa and surrounding commits

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: James Almer <jamrial@gmail.com>

tools/target_dec_fuzzer.c

@@ -47,6 +47,7 @@
 
 #include "config.h"
 #include "libavutil/avassert.h"
+#include "libavutil/avstring.h"
 #include "libavutil/cpu.h"
 #include "libavutil/imgutils.h"
 #include "libavutil/intreadwrite.h"
@@ -273,7 +274,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
         extradata_size = bytestream2_get_le32(&gbc);
 
         ctx->sample_rate                        = bytestream2_get_le32(&gbc) & 0x7FFFFFFF;
-        ctx->ch_layout.channels                 = (unsigned)bytestream2_get_le32(&gbc) % FF_SANE_NB_CHANNELS;
+        ctx->ch_layout.nb_channels              = (unsigned)bytestream2_get_le32(&gbc) % FF_SANE_NB_CHANNELS;
         ctx->block_align                        = bytestream2_get_le32(&gbc) & 0x7FFFFFFF;
         ctx->codec_tag                          = bytestream2_get_le32(&gbc);
         if (c->codec_tags) {