HDRenderPipeline: Fix an issue with tessellation when in heightmap min > max

- min can be > max when baking a high poly mesh on a bigger low poly
mesh, in this case the culling must not fail

ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/LitData.hlsl

 {
     float maxDisplacement = 0.0;
 #if defined(_HEIGHTMAP)
-    maxDisplacement = _HeightAmplitude;
+    maxDisplacement = abs(_HeightAmplitude); // _HeightAmplitude can be negative if min and max are inverted, but the max displacement must be positive
 #endif
     return maxDisplacement;
 }
 {
     float maxDisplacement = 0.0;
 
+    // _HeightAmplitudeX can be negative if min and max are inverted, but the max displacement must be positive, take abs()
-    maxDisplacement = _HeightAmplitude0;
+    maxDisplacement = abs(_HeightAmplitude0);
-    maxDisplacement = max(  _HeightAmplitude1
+    maxDisplacement = max(  abs(_HeightAmplitude1)
-                            +_HeightAmplitude0 * _InheritBaseHeight1
+                            +_abs(HeightAmplitude0) * _InheritBaseHeight1
                             #endif
                             , maxDisplacement);
 #endif
-    maxDisplacement = max(  _HeightAmplitude2
+    maxDisplacement = max(  abs(_HeightAmplitude2)
-                            +_HeightAmplitude0 * _InheritBaseHeight2
+                            + abs(HeightAmplitude0) * _InheritBaseHeight2
                             #endif
                             , maxDisplacement);
 #endif
 #if defined(_HEIGHTMAP3)
-    maxDisplacement = max(  _HeightAmplitude3
+    maxDisplacement = max(  abs(_HeightAmplitude3)
-                            +_HeightAmplitude0 * _InheritBaseHeight3
+                            + abs(HeightAmplitude0) * _InheritBaseHeight3
                             #endif
                             , maxDisplacement);
 #endif