ShaderGen: Support writing integer colors when logic op is enabled

This is required for D3D to support logic op.

Source/Core/VideoCommon/BPMemory.cpp

@@ -10,6 +10,19 @@
 // STATE_TO_SAVE
 BPMemory bpmem;
 
+bool BlendMode::UseLogicOp() const
+{
+  // Logicop bit has lowest priority.
+  if (subtract || blendenable || !logicopenable)
+    return false;
+
+  // Fast path for Kirby's Return to Dreamland, they use it with dstAlpha.
+  if (logicmode == BlendMode::NOOP)
+    return false;
+
+  return true;
+}
+
 float FogParam0::GetA() const
 {
   // scale mantissa from 11 to 23 bits