LightingShaderGen: Always calculate lighting for both color channels

Cel-damage uses the color from the lighting stage of the vertex pipeline
as texture coordinates, but sets numColorChans to zero.

We now calculate the colors in all cases, but override the color before
writing it from the vertex shader if numColorChans is set to a lower value.

Source/Core/VideoCommon/VertexShaderGen.cpp

@@ -239,24 +239,8 @@ ShaderCode GenerateVertexShaderCode(APIType api_type, const ShaderHostConfig& ho
             "float3 ldir, h, cosAttn, distAttn;\n"
             "float dist, dist2, attn;\n");
 
-  if (uid_data->numColorChans == 0)
-  {
-    if (uid_data->components & VB_HAS_COL0)
-      out.Write("o.colors_0 = rawcolor0;\n");
-    else
-      out.Write("o.colors_0 = float4(1.0, 1.0, 1.0, 1.0);\n");
-  }
-
-  GenerateLightingShaderCode(out, uid_data->lighting, uid_data->components, uid_data->numColorChans,
-                             "rawcolor", "o.colors_");
-
-  if (uid_data->numColorChans < 2)
-  {
-    if (uid_data->components & VB_HAS_COL1)
-      out.Write("o.colors_1 = rawcolor1;\n");
-    else
-      out.Write("o.colors_1 = o.colors_0;\n");
-  }
+  GenerateLightingShaderCode(out, uid_data->lighting, uid_data->components, "rawcolor",
+                             "o.colors_");
 
   // transform texcoords
   out.Write("float4 coord = float4(0.0, 0.0, 1.0, 1.0);\n");
@@ -398,6 +382,21 @@ ShaderCode GenerateVertexShaderCode(APIType api_type, const ShaderHostConfig& ho
     out.Write("}\n");
   }
 
+  if (uid_data->numColorChans == 0)
+  {
+    if (uid_data->components & VB_HAS_COL0)
+      out.Write("o.colors_0 = rawcolor0;\n");
+    else
+      out.Write("o.colors_0 = float4(1.0, 1.0, 1.0, 1.0);\n");
+  }
+  if (uid_data->numColorChans < 2)
+  {
+    if (uid_data->components & VB_HAS_COL1)
+      out.Write("o.colors_1 = rawcolor1;\n");
+    else
+      out.Write("o.colors_1 = o.colors_0;\n");
+  }
+
   // clipPos/w needs to be done in pixel shader, not here
   out.Write("o.clipPos = o.pos;\n");