[HLSL/Spir-V] fix for incorrect spir-v on int dot(int, int)

Decomposes OpDot into corresponding multiplies and additions.

Test/hlsl.int.dot.frag

@@ -0,0 +1,14 @@
+float4 main() : SV_Target {
+  int i = 1;
+  int1 i2 = 2;
+  int2 i3 = 3;
+  int3 i4 = 4;
+  int4 i5 = 5;
+
+  i = dot(i, i);
+  i2 = dot(i2, i2);
+  i3 = dot(i3, i3);
+  i4 = dot(i4, i4);
+  i5 = dot(i5, i5);
+  return i + i2.xxxx + i3.xyxy + i4.xyzx + i5;
+}