avcodec/libfdk-aacdec: fix the check for downmix layout order

The code reads a mask afer this check, meaning it expects NATIVE order, not
others.

Signed-off-by: James Almer <jamrial@gmail.com>
(cherry picked from commit 7755d264bd)

libavcodec/libfdk-aacdec.c

@@ -269,7 +269,7 @@ static av_cold int fdk_aac_decode_init(AVCodecContext *avctx)
     }
 
     if (s->downmix_layout.nb_channels > 0 &&
-        s->downmix_layout.order != AV_CHANNEL_ORDER_NATIVE) {
+        s->downmix_layout.order == AV_CHANNEL_ORDER_NATIVE) {
         int downmix_channels = -1;
 
         switch (s->downmix_layout.u.mask) {