mlkem: poly.jinc update from formosa-crypto/formosa-mlkem#20 (single it. var. get_noise)

Author: tfaoliveira

src/crypto_kem/mlkem/mlkem768/amd64/ref/poly.jinc

@@ -144,23 +144,21 @@ fn _poly_compress(reg u64 rp, reg ptr u16[MLKEM_N] a) -> reg ptr u16[MLKEM_N]
 {
   reg u16 t;
   reg u32 d0, d1;
-  reg u64 i j;
+  reg u64 i;
 
   a = _poly_csubq(a);
 
   i = 0;
-  j = 0;
   while(i < 128)
   {
-    t  = a[(int)j];
+    t  = a[2 * i];
     d0 = (32u)t;
     d0 <<= 4;
     d0 += 1665;
     d0 *= 80635;
     d0 >>= 28;
     d0 &= 0xf;
-    j += 1;
-    t  = a[(int)j];
+    t  = a[2 * i + 1];
     d1 = (32u)t;
     d1 <<= 4;
     d1 += 1665;
@@ -171,7 +169,6 @@ fn _poly_compress(reg u64 rp, reg ptr u16[MLKEM_N] a) -> reg ptr u16[MLKEM_N]
     d0 |= d1;
     (u8)[rp+i] = d0;
     i += 1;
-    j += 1;
   }
   return a;
 }