libfdk-aacdec: Bump the max number of channels to 8

In the latest version of fdk-aac, the decoder can output up to 8
channels; take this into account when preallocating buffers that
need to fit the output from any packet.

CC: libav-stable@libav.org
Signed-off-by: NMartin Storsjö <martin@martin.st>

libavcodec/libfdk-aacdec.c

@@ -54,7 +54,7 @@ typedef struct FDKAACDecContext {
 
 
 #define DMX_ANC_BUFFSIZE       128
-#define DECODER_MAX_CHANNELS     6
+#define DECODER_MAX_CHANNELS     8
 #define DECODER_BUFFSIZE      2048 * sizeof(INT_PCM)
 
 #define OFFSET(x) offsetof(FDKAACDecContext, x)