Clarify this is HSA only.

Author: AlexVlx

llvm/docs/ReleaseNotes.md

@@ -85,7 +85,7 @@ Changes to the AMDGPU Backend
 
 * Enabled the
   [FWD_PROGRESS bit](https://llvm.org/docs/AMDGPUUsage.html#code-object-v3-kernel-descriptor)
-  for all GFX ISAs greater or equal to 10
+  for all GFX ISAs greater or equal to 10, for the AMDHSA OS.
 
 Changes to the ARM Backend
 --------------------------