[Vulkan] Fix stacked-texture inter-layer lerp base in SampleTexture

Co-authored-by: Herman S. <429230+has207@users.noreply.github.com>

src/xenia/gpu/spirv_shader_translator.h

@@ -34,7 +34,7 @@ class SpirvShaderTranslator : public ShaderTranslator {
     // TODO(Triang3l): Change to 0xYYYYMMDD once it's out of the rapid
     // prototyping stage (easier to do small granular updates with an
     // incremental counter).
-    static constexpr uint32_t kVersion = 10;
+    static constexpr uint32_t kVersion = 11;
 
     enum class DepthStencilMode : uint32_t {
       kNoModifiers,

src/xenia/gpu/spirv_shader_translator_fetch.cc

@@ -2651,7 +2651,7 @@ void SpirvShaderTranslator::SampleTexture(
                                                  sign_result, lerp_first),
               lerp_factor);
           sign_result = builder_->createNoContractionBinOp(
-              spv::OpFAdd, type_float4_, sign_result, lerp_difference);
+              spv::OpFAdd, type_float4_, lerp_first, lerp_difference);
         }
       }
     }