avcodec/aacpsdsp_template: Fix integer overflow in ps_stereo_interpolate_c()

Fixes: signed integer overflow: -1813244069 + -1407981383 cannot be represented in type 'int'
Fixes: 8823/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_AAC_FIXED_fuzzer-5643295618236416

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/aacpsdsp_template.c

@@ -150,10 +150,10 @@ static void ps_stereo_interpolate_c(INTFLOAT (*l)[2], INTFLOAT (*r)[2],
     INTFLOAT h1 = h[0][1];
     INTFLOAT h2 = h[0][2];
     INTFLOAT h3 = h[0][3];
-    INTFLOAT hs0 = h_step[0][0];
-    INTFLOAT hs1 = h_step[0][1];
-    INTFLOAT hs2 = h_step[0][2];
-    INTFLOAT hs3 = h_step[0][3];
+    UINTFLOAT hs0 = h_step[0][0];
+    UINTFLOAT hs1 = h_step[0][1];
+    UINTFLOAT hs2 = h_step[0][2];
+    UINTFLOAT hs3 = h_step[0][3];
     int n;
 
     for (n = 0; n < len; n++) {