Suppress a few common but harmless warnings in FFX's HLSL code.

This way we don't have to modify the FSR2 shaders to get rid of these warnings.

Assets/Resources/FSR2/ffx_fsr2_unity_common.cginc

@@ -1,4 +1,8 @@
-#define FFX_GPU         // Compiling for GPU
+// Suppress a few warnings produced by FFX's HLSL code
+#pragma warning(disable: 3078)      // Loop control variable conflicts
+#pragma warning(disable: 3203)      // Signed/unsigned mismatch
+
+#define FFX_GPU         // Compiling for GPU
 #define FFX_HLSL        // Compile for plain HLSL
 
 // Use the DXC shader compiler on modern graphics APIs to enable a few advanced features