avcodec/g723_1dec: Clip bits2 in both directions

Fixes: shift exponent 33 is too large for 32-bit type 'int'
Fixes: 6743/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_G723_1_fuzzer-5823772687859712

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 53f241218d)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/g723_1dec.c

@@ -549,7 +549,7 @@ static void gain_scale(G723_1_Context *p, int16_t * buf, int energy)
         denom <<= bits2;
 
         bits2 = 5 + bits1 - bits2;
-        bits2 = FFMAX(0, bits2);
+        bits2 = av_clip_uintp2(bits2, 5);
 
         gain = (num >> 1) / (denom >> 16);
         gain = square_root(gain << 16 >> bits2);