SWDEV-521647 - Fix tracking of hw_event (#206)

- When a command may possibly have two packets(like device heap
  initializer), and if there is no signal on the main kernel packet the
tracking was broken as it marked HW event of the command as the first
packet signal.
- Make sure if no completion signal is attached to the second packet
  then clear the HW event for the command.

rocclr/device/rocm/rocvirtual.hpp

@@ -254,7 +254,7 @@ class VirtualGPU : public device::VirtualDevice {
 
     //! Finds a free signal for the upcomming operation
     hsa_signal_t ActiveSignal(hsa_signal_value_t init_val = kInitSignalValueOne,
-                              Timestamp* ts = nullptr);
+                              Timestamp* ts = nullptr, bool attach_signal = true);
 
     //! Wait for the curent active signal. Can idle the queue
     bool WaitCurrent() {