aacenc: mark the preset 5.0/5.1 layouts correctly with back speakers

The spec is correct, it does list these layouts as having rear speakers.
Questionable how many decoders correctly interpret those correctly since
side is way more popular.
Also fixes fate-aac-yoraw-encode.

Reported-by: pkviet <pkv.stream@gmail.com>
Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>

libavcodec/aacenctab.h

@@ -49,8 +49,8 @@ static const int64_t aac_normal_chan_layouts[7] = {
     AV_CH_LAYOUT_STEREO,
     AV_CH_LAYOUT_SURROUND,
     AV_CH_LAYOUT_4POINT0,
-    AV_CH_LAYOUT_5POINT0,
-    AV_CH_LAYOUT_5POINT1,
+    AV_CH_LAYOUT_5POINT0_BACK,
+    AV_CH_LAYOUT_5POINT1_BACK,
     AV_CH_LAYOUT_7POINT1,
 };