[wsi] Move DxvkWindowState to wsi platform header

src/wsi/win32/wsi_platform_win32.h

@@ -0,0 +1,16 @@
+#pragma once
+
+#include <windows.h>
+
+namespace dxvk::wsi {
+
+  /**
+    * \brief Impl-dependent state
+    */
+  struct DxvkWindowState {
+    LONG style   = 0;
+    LONG exstyle = 0;
+    RECT rect    = { 0, 0, 0, 0 };
+  };
+
+}

src/wsi/wsi_platform.h

@@ -0,0 +1,5 @@
+#pragma once
+
+#ifdef DXVK_WSI_WIN32
+#include "win32/wsi_platform_win32.h"
+#endif

src/wsi/wsi_window.h

@@ -3,22 +3,12 @@
 #include <windows.h>
 
 #include "wsi_monitor.h"
+#include "wsi_platform.h"
 
 #include "../vulkan/vulkan_loader.h"
 
 namespace dxvk::wsi {
 
-  /**
-    * \brief Impl-dependent state
-    */
-  struct DxvkWindowState {
-#ifdef DXVK_WSI_WIN32
-    LONG style   = 0;
-    LONG exstyle = 0;
-    RECT rect    = { 0, 0, 0, 0 };
-#endif
-  };
-
   /**
     * \brief The size of the window
     *