shader_conversion: I2F : add Assert for case src_size is Short

src/video_core/shader/decode/conversion.cpp

@@ -86,6 +86,9 @@ u32 ShaderIR::DecodeConversion(NodeBlock& bb, u32 pc) {
         if (const u32 offset = static_cast<u32>(instr.conversion.int_src.selector); offset > 0) {
             ASSERT(instr.conversion.src_size == Register::Size::Byte ||
                    instr.conversion.src_size == Register::Size::Short);
+            if (instr.conversion.src_size == Register::Size::Short) {
+                ASSERT(offset == 0 || offset == 2);
+            }
             value = SignedOperation(OperationCode::ILogicalShiftRight, input_signed,
                                     std::move(value), Immediate(offset * 8));
         }