[dxvk] Factor out waiting for resource to become idle

And use the new generic spin function to reduce syscall spam.

src/d3d11/d3d11_context_imm.cpp

@@ -616,8 +616,7 @@ namespace dxvk {
         Flush();
         SynchronizeCsThread();
         
-        while (Resource->isInUse(access))
-          dxvk::this_thread::yield();
+        Resource->waitIdle(access);
       }
     }
     

src/d3d9/d3d9_device.cpp

@@ -3779,8 +3779,7 @@ namespace dxvk {
         Flush();
         SynchronizeCsThread();
 
-        while (Resource->isInUse(access))
-          dxvk::this_thread::yield();
+        Resource->waitIdle(access);
       }
     }
 

src/dxvk/dxvk_resource.h

@@ -69,6 +69,19 @@ namespace dxvk {
           : m_useCountW) -= 1;
       }
     }
+
+    /**
+     * \brief Waits for resource to become unused
+     *
+     * Blocks calling thread until the GPU finishes
+     * using the resource with the given access type.
+     * \param [in] access Access type to check for
+     */
+    void waitIdle(DxvkAccess access = DxvkAccess::Read) const {
+      sync::spin(50000, [this, access] {
+        return !isInUse(access);
+      });
+    }
     
   private: