Fix inconsistency of diffusion profile int -> uint

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/Lit/Lit.cs

             // SpecularColor fold into fresnel0
 
             // SSS
-            public int diffusionProfile;
+            public uint diffusionProfile;
             public float subsurfaceMask;
 
             // Transmission

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/Lit/Lit.cs.hlsl

     float metallic;
     float coatMask;
     float3 specularColor;
-    int diffusionProfile;
+    uint diffusionProfile;
     float subsurfaceMask;
     float thickness;
     float3 tangentWS;