[HDRP] Make Decal shader compatible with SRP batcher (#3806)

* Fix SRP batcher with decal

* Update CHANGELOG.md

* Update CHANGELOG.md

Author: sebastienlagarde

com.unity.render-pipelines.high-definition/CHANGELOG.md

@@ -51,6 +51,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed SSGI frame setting not greyed out while SSGI is disabled in HDRP Asset
 - Fixed HDRP material being constantly dirty.
 - Fixed issue in path tracing, where objects would cast shadows even if not present in the path traced layers (case 1318857).
+- Fixed SRP batcher not compatible with Decal (case 1311586)
 
 ### Changed
 - Updated the tooltip for the Decal Angle Fade property (requires to enable Decal Layers in both HDRP asset and Frame settings) (case 1308048).

com.unity.render-pipelines.high-definition/Runtime/Material/Decal/DecalProperties.hlsl

@@ -10,6 +10,8 @@ SAMPLER(sampler_MaskMap);
 TEXTURE2D(_EmissiveColorMap);
 SAMPLER(sampler_EmissiveColorMap);
 
+CBUFFER_START(UnityPerMaterial)
+
 float _NormalBlendSrc;
 float _MaskBlendSrc;
 float _DecalBlend;
@@ -35,4 +37,6 @@ float _Metallic;
     float4 _SelectionID;
 #endif
 
+CBUFFER_END
+
 #endif