Add a threshold for forcing ROCr to take blit path

This workaround is to avoid performance penalty of SDMA engine
taking a while to clock up from a lower DPM state. Add env var
GPU_FORCE_BLIT_COPY_SIZE (1024 by default for HIP in KB). Forcing
Src and Dst agent to be amdgpu makes ROCr take blit copy path for
what otherwise should have been SDMA copy

Change-Id: I222f687155f86000d17d66d25182e490b6710463


[ROCm/clr commit: 5f64e6e7ad]

projects/clr/rocclr/device/rocm/rocsettings.cpp

@@ -74,6 +74,8 @@ Settings::Settings() {
   pinnedXferSize_ = std::min(GPU_PINNED_XFER_SIZE, MaxPinnedXferSize) * Mi;
   pinnedMinXferSize_ = std::min(GPU_PINNED_MIN_XFER_SIZE * Ki, pinnedXferSize_);
 
+  sdmaCopyThreshold_ = GPU_FORCE_BLIT_COPY_SIZE * Ki;
+
   // Don't support Denormals for single precision by default
   singleFpDenorm_ = false;