headers: Remove obsolete references to vulkan.h

Change-Id: I214dc6d3e7dbe256b9584896e78e30a67d71d5c6
diff --git a/include/vulkan/vk_icd.h b/include/vulkan/vk_icd.h
index 35956a3..29b077b 100644
--- a/include/vulkan/vk_icd.h
+++ b/include/vulkan/vk_icd.h
@@ -23,7 +23,7 @@
 #ifndef VKICD_H
 #define VKICD_H
 
-#include "vulkan.h"
+#include "vulkan_core.h"
 #include <stdbool.h>
 
 // Loader-ICD version negotiation API.  Versions add the following features:
diff --git a/include/vulkan/vk_layer.h b/include/vulkan/vk_layer.h
index e8300c3..645a4b0 100644
--- a/include/vulkan/vk_layer.h
+++ b/include/vulkan/vk_layer.h
@@ -26,7 +26,7 @@
  */
 #pragma once
 
-#include "vulkan.h"
+#include "vulkan_core.h"
 #if defined(__GNUC__) && __GNUC__ >= 4
 #define VK_LAYER_EXPORT __attribute__((visibility("default")))
 #elif defined(__SUNPRO_C) && (__SUNPRO_C >= 0x590)