[Opus] Update to v1.2.1

third_party/opus/src/silk/float/k2a_FLP.c

Index: third_party/opus/src/silk/float/k2a_FLP.c
diff --git a/third_party/opus/src/silk/float/k2a_FLP.c b/third_party/opus/src/silk/float/k2a_FLP.c
index 12af4e76697a869831b73de533e316a8859b8163..1448008dbbed139791089132b0e391b2e7e07f6b 100644
--- a/third_party/opus/src/silk/float/k2a_FLP.c
+++ b/third_party/opus/src/silk/float/k2a_FLP.c
@@ -39,15 +39,16 @@ void silk_k2a_FLP(
 )
 {
     opus_int   k, n;
-    silk_float Atmp[ SILK_MAX_ORDER_LPC ];
+    silk_float rck, tmp1, tmp2;
 
     for( k = 0; k < order; k++ ) {
-        for( n = 0; n < k; n++ ) {
-            Atmp[ n ] = A[ n ];
+        rck = rc[ k ];
+        for( n = 0; n < (k + 1) >> 1; n++ ) {
+            tmp1 = A[ n ];
+            tmp2 = A[ k - n - 1 ];
+            A[ n ]         = tmp1 + tmp2 * rck;
+            A[ k - n - 1 ] = tmp2 + tmp1 * rck;
         }
-        for( n = 0; n < k; n++ ) {
-            A[ n ] += Atmp[ k - n - 1 ] * rc[ k ];
-        }
-        A[ k ] = -rc[ k ];
+        A[ k ] = -rck;
     }
 }