Force enable FP16 shader code path, and redefine FFXM_HALF with a truthy value

Packages/com.unity.postprocessing@3.2.2/PostProcessing/Runtime/Effects/Upscaling/ASR/Runtime/AsrContext.cs

@@ -52,6 +52,7 @@ namespace ArmASR
         public void Create(in Asr.ContextDescription contextDescription)
         {
             _contextDescription = contextDescription;
+            _contextDescription.Flags |= Asr.InitializationFlags.EnableFP16Usage;   // Always force FP16 code path
             
             _upscalerConstantsBuffer = CreateConstantBuffer<Asr.UpscalerConstants>();
             _spdConstantsBuffer = CreateConstantBuffer<Asr.SpdConstants>();

Packages/com.unity.postprocessing@3.2.2/PostProcessing/Runtime/Effects/Upscaling/ASR/Shaders/ffxm_fsr2_common.cginc

@@ -4,6 +4,10 @@
 #pragma warning(disable: 3556)      // Integer divides might be much slower, try using uints if possible
 
 // If these keywords are set by Unity, redefine them to have a truthy value
+#if defined(FFXM_HALF)
+#undef FFXM_HALF
+#define FFXM_HALF   (1)
+#endif
 #ifdef FFXM_FSR2_OPTION_SHADER_OPT_PERFORMANCE
 #undef FFXM_FSR2_OPTION_SHADER_OPT_PERFORMANCE
 #define FFXM_FSR2_OPTION_SHADER_OPT_PERFORMANCE 1