[PlanarReflection] fix cache type check

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Lighting/LightLoop/LightLoopDef.hlsl

     // This code will be inlined as lightLoopContext is hardcoded in the light loop
     if (lightLoopContext.sampleReflection == SINGLE_PASS_CONTEXT_SAMPLE_REFLECTION_PROBES)
     {
-        if (index == ENVCACHETYPE_TEXTURE2D)
+        if (cacheType == ENVCACHETYPE_TEXTURE2D)
-        else if (index == ENVCACHETYPE_CUBEMAP)
+        else if (cacheType == ENVCACHETYPE_CUBEMAP)
             return SAMPLE_TEXTURECUBE_ARRAY_LOD_ABSTRACT(_EnvCubemapTextures, s_trilinear_clamp_sampler, texCoord, index, lod);
         return float4(0, 0, 0, 0);
     }