loader: Fixes for ICD vk{Create|Destroy}SurfaceKHR

Need to keep VkIcdSurface private to the loader.

The definition may conflict with some redefinitions of
VK_DEFINE_NON_DISPATCHABLE_HANDLE and it's not necessary to make public
anyway.

Change-Id: I30e166f0ecce2fd3ea36c745dc073b705973d75f
diff --git a/loader/loader.h b/loader/loader.h
index a65f489..060e02e 100644
--- a/loader/loader.h
+++ b/loader/loader.h
@@ -511,6 +511,7 @@
                                              uint32_t *icd_index);
 void loader_init_dispatch_dev_ext(struct loader_instance *inst,
                                   struct loader_device *dev);
+VKAPI_ATTR PFN_vkVoidFunction VKAPI_CALL loader_gpa_device_internal(VkDevice device, const char *pName);
 void *loader_dev_ext_gpa(struct loader_instance *inst, const char *funcName);
 void *loader_get_dev_ext_trampoline(uint32_t index);
 struct loader_instance *loader_get_instance(const VkInstance instance);