vulkan/device-select-layer: Include vulkan.h

In the upcoming header update, vk_layer.h starts including vulkan_core.h
instead of vulkan.h.  This will break this layer as it needs a couple of
window-system extension #defines.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21225>

src/vulkan/device-select-layer/device_select_layer.c

@@ -30,6 +30,7 @@
  */
 
 #include <vulkan/vk_layer.h>
+#include <vulkan/vulkan.h>
 
 #include <assert.h>
 #include <stdio.h>