avcodec/ac3enc: silence 2 warnings about "possibly uninitialized" variables

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/ac3enc.c

@@ -1381,7 +1381,7 @@ static void ac3_output_frame_header(AC3EncodeContext *s)
  */
 static void output_audio_block(AC3EncodeContext *s, int blk)
 {
-    int ch, i, baie, bnd, got_cpl, ch0;
+    int ch, i, baie, bnd, got_cpl, av_uninit(ch0);
     AC3Block *block = &s->blocks[blk];
 
     /* block switching */
@@ -2246,7 +2246,7 @@ static av_cold int validate_options(AC3EncodeContext *s)
  */
 static av_cold void set_bandwidth(AC3EncodeContext *s)
 {
-    int blk, ch, cpl_start;
+    int blk, ch, av_uninit(cpl_start);
 
     if (s->cutoff) {
         /* calculate bandwidth based on user-specified cutoff frequency */