loader: Fix 32-bit loader exception when layers enabled for Vulkan apps.

The loader_create_device_terminator had an incorrect calling convention.  This
caused the ESP pointer to not get properly restored after the function was
called by a 32-bit application.
diff --git a/loader/loader.c b/loader/loader.c
index 9040f3f..1b8fe21 100644
--- a/loader/loader.c
+++ b/loader/loader.c
@@ -2987,7 +2987,7 @@
     return err;
 }
 
-VkResult loader_create_device_terminator(
+VKAPI_ATTR VkResult VKAPI_CALL loader_create_device_terminator(
         VkPhysicalDevice                            physicalDevice,
         const VkDeviceCreateInfo*                   pCreateInfo,
         const VkAllocationCallbacks*                pAllocator,