Fixed spot light angle attenuation. Now it matches legacy Unity. Not exposing now innerCone angle due to LW not supporting additional light component.

ScriptableRenderPipeline/LightweightPipeline/LightweightPipeline.cs

 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using UnityEngine.Experimental.GlobalIllumination;
 using UnityEngine.Rendering;
 using UnityEngine.Rendering.PostProcessing;
 using UnityEngine.XR;
 
             BuildShadowSettings();
             SetRenderingFeatures();
-            GraphicsSettings.lightsUseLinearIntensity = true;
 
             PerFrameBuffer._GlossyEnvironmentColor = Shader.PropertyToID("_GlossyEnvironmentColor");
             PerFrameBuffer._SubtractiveShadowColor = Shader.PropertyToID("_SubtractiveShadowColor");
         {
             base.Render(context, cameras);
 
+            GraphicsSettings.lightsUseLinearIntensity = true;
             SetupPerFrameShaderConstants();
 
             // Sort cameras array by camera depth
                 // invAngleRange = 1.0 / (cosInnerAngle - cosOuterAngle)
                 // SdotL * invAngleRange + (-cosOuterAngle * invAngleRange)
                 // If we precompute the terms in a MAD instruction
-                float spotAngle = Mathf.Deg2Rad * lightData.spotAngle;
-                float cosOuterAngle = Mathf.Cos(spotAngle * 0.5f);
-                float cosInneAngle = Mathf.Cos(spotAngle * 0.25f);
-                float smoothAngleRange = cosInneAngle - cosOuterAngle;
-                if (Mathf.Approximately(smoothAngleRange, 0.0f))
-                    smoothAngleRange = 1.0f;
-
+                float cosOuterAngle = Mathf.Cos(Mathf.Deg2Rad * lightData.spotAngle * 0.5f);
+                float cosInneAngle = Mathf.Cos(LightmapperUtils.ExtractInnerCone(lightData.light) * 0.5f);
+                float smoothAngleRange = Mathf.Max(0.001f, cosInneAngle - cosOuterAngle);
                 float invAngleRange = 1.0f / smoothAngleRange;
                 float add = -cosOuterAngle * invAngleRange;
                 lightSpotAttenuation = new Vector4(invAngleRange, add, 0.0f);

ScriptableRenderPipeline/LightweightPipeline/Shaders/LightweightShaderLibrary/Lighting.hlsl

 
     // If we precompute the terms in a MAD instruction
     half SdotL = dot(spotDirection, lightDirection);
-    return saturate(SdotL * spotAttenuation.x + spotAttenuation.y);
+    half atten = saturate(SdotL * spotAttenuation.x + spotAttenuation.y);
+    return atten * atten;
 }
 
 inline half GetLightDirectionAndRealtimeAttenuation(LightInput lightInput, half3 normal, float3 worldPos, out half3 lightDirection)