Fix unused HDFirearm function and repurpose it for fixing staggered fire

Author: fourZK

Entities/AHuman.cpp

@@ -3306,6 +3306,8 @@ void AHuman::Update()
 							if (deviceAsFirearm->FiredOnce()) {
 								m_CanActivateBGItem = true;
 								m_TriggerPulled = true;
+							} else {
+								m_CanActivateBGItem = !deviceAsFirearm->CanFire();
 							}
 						}
 					}
@@ -3402,6 +3404,8 @@ void AHuman::Update()
 					if (deviceAsFirearm->FiredOnce()) {
 						m_CanActivateBGItem = false;
 						m_TriggerPulled = true;
+					} else {
+						m_CanActivateBGItem = deviceAsFirearm->CanFire();
 					}
 				}
 			} else {

Entities/HDFirearm.h

@@ -821,7 +821,7 @@ AddScriptFunctionNames(HeldDevice, "OnFire", "OnReload");
 	/// Gets whether this HDFirearm is ready to be fired.
 	/// </summary>
 	/// <returns>Whether this HDFirearm is ready to pop another Round.</returns>
-	bool CanFire() const { return m_ActivationTimer.IsPastSimMS(GetMSPerRound()); }
+	bool CanFire() const { return m_LastFireTmr.IsPastSimMS(GetMSPerRound()); }
 
 	/// <summary>
 	/// Gets whether this HDFirearm is halfway to be fired. Used for evenly spacing out dual-wielded fire.