dev-amdgpu: Forward RLC queue doorbells

Forward user queue doorbells to the SDMA. This is the final step needed
to enable RLC (user) queues to replace BLIT kernels.

Change-Id: I0c2ef70bb5414b82785ef437dd65d6c57798d24f
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/63033
Maintainer: Matt Sinclair <mattdsinclair@gmail.com>
Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/dev/amdgpu/amdgpu_device.cc

@@ -297,8 +297,8 @@ AMDGPUDevice::writeDoorbell(PacketPtr pkt, Addr offset)
             deviceIH->updateRptr(pkt->getLE<uint32_t>());
             break;
           case RLC: {
-            panic("RLC queues not yet supported. Run with the environment "
-                  "variable HSA_ENABLE_SDMA set to False");
+            SDMAEngine *sdmaEng = getSDMAEngine(offset);
+            sdmaEng->processRLC(offset, pkt->getLE<uint64_t>());
           } break;
           default:
             panic("Write to unkown queue type!");