[vulkan] relax warning about exclusive fullscreen

Only warn if it's actually available.

src/vulkan/vulkan_presenter.cpp

@@ -14,7 +14,7 @@ namespace dxvk::vk {
     // As of Wine 5.9, winevulkan provides this extension, but does
     // not filter the pNext chain for VkSwapchainCreateInfoKHR properly
     // before passing it to the Linux sude, which breaks RenderDoc.
-    if (::GetModuleHandle("winevulkan.dll")) {
+    if (m_device.features.fullScreenExclusive && ::GetModuleHandle("winevulkan.dll")) {
       Logger::warn("winevulkan detected, disabling exclusive fullscreen support");
       m_device.features.fullScreenExclusive = false;
     }