gl_shader_decompiler: Properly emulate NaN behaviour on NE

"Not equal" operators on GLSL seem to behave as unordered when we expect
an ordered comparison.

Manually emulate this checking for LGE values (numbers, not-NaNs).

src/video_core/renderer_opengl/gl_shader_decompiler.cpp

@@ -1845,6 +1845,15 @@ private:
         static_assert(!unordered || type == Type::Float);
 
         const Expression expr = GenerateBinaryInfix(operation, op, Type::Bool, type, type);
+
+        if constexpr (op.compare("!=") == 0 && type == Type::Float && !unordered) {
+            // GLSL's operator!=(float, float) doesn't seem be ordered. This happens on both AMD's
+            // and Nvidia's proprietary stacks. Manually force an ordered comparison.
+            return {fmt::format("({} && !isnan({}) && !isnan({}))", expr.AsBool(),
+                                VisitOperand(operation, 0).AsFloat(),
+                                VisitOperand(operation, 1).AsFloat()),
+                    Type::Bool};
+        }
         if constexpr (!unordered) {
             return expr;
         }