address some PR comments

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Decal/DecalSystem.cs

 
             void UpdateTextureCache(CommandBuffer cmd)
             {
-                if ((m_DiffuseTexIndex == -1) && (m_DiffuseTexture != null))
+                if (m_DiffuseTexture != null)
-                if ((m_NormalTexIndex == -1) && (m_NormalTexture != null))
+                else
+                {
+                    m_DiffuseTexIndex = -1;
+                }
+
+                if (m_NormalTexture != null)
-                if ((m_MaskTexIndex == -1) && (m_MaskTexture != null))
+                else
+                {
+                    m_NormalTexIndex = -1;
+                }
+
+                if (m_MaskTexture != null)
+                }
+                else
+                {
+                    m_MaskTexIndex = -1;
                 }
             }
 

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/Decal/Decal.hlsl

 TEXTURE2D_ARRAY(_DecalAtlas);          
 SAMPLER(sampler_DecalAtlas);
 
-// define these specifically for decal normal map sampling to not be dependent on surface gradient
-#if defined(UNITY_NO_DXT5nm)
-#define DECAL_UNPACK_NORMAL_FUNC UnpackNormalRGB
-#else
-#define DECAL_UNPACK_NORMAL_FUNC UnpackNormalmapRGorAG
-#endif
-
 // Must be in sync with RT declared in HDRenderPipeline.cs ::Rebuild
 void EncodeIntoDBuffer( DecalSurfaceData surfaceData,
                         out DBufferType0 outDBuffer0,

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/Decal/DecalData.hlsl

 	surfaceData.HTileMask |= DBUFFERHTILEBIT_DIFFUSE;
 #endif
 #if _NORMALMAP
-	surfaceData.normalWS.xyz = mul((float3x3)decalToWorld, DECAL_UNPACK_NORMAL_FUNC(SAMPLE_TEXTURE2D(_NormalMap, sampler_NormalMap, texCoordDS))) * 0.5f + 0.5f;
+	surfaceData.normalWS.xyz = mul((float3x3)decalToWorld, UnpackNormalmapRGorAG(SAMPLE_TEXTURE2D(_NormalMap, sampler_NormalMap, texCoordDS))) * 0.5f + 0.5f;
 	surfaceData.normalWS.w = totalBlend;
 	surfaceData.HTileMask |= DBUFFERHTILEBIT_NORMAL;
 #endif

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/Decal/DecalUtilities.hlsl

 void ApplyBlendNormal(inout float4 dst, inout int matMask, float2 texCoords, int sliceIndex, int mapMask, float3x3 decalToWorld, float blend)
 {
 	float4 src;
-	src.xyz =  mul(decalToWorld, DECAL_UNPACK_NORMAL_FUNC(SAMPLE_TEXTURE2D_ARRAY(_DecalAtlas, sampler_DecalAtlas, texCoords, sliceIndex))) * 0.5f + 0.5f;
+	src.xyz =  mul(decalToWorld, UnpackNormalmapRGorAG(SAMPLE_TEXTURE2D_ARRAY(_DecalAtlas, sampler_DecalAtlas, texCoords, sliceIndex))) * 0.5f + 0.5f;
 	src.w = blend;
 	dst.xyz = src.xyz * src.w + dst.xyz * (1.0f - src.w);
 	dst.w = dst.w * (1.0f - src.w);