anv: error out if anv_genX.h is included by !anv_private.h

Update the comment to reflect the correct filename and add a guard to
catch incorrect inclusion of the header.

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Chad Versace <chadversary@chromium.org>

src/intel/vulkan/anv_genX.h

@@ -27,11 +27,15 @@
 
 /*
  * Gen-specific function declarations.  This header must *not* be included
- * directly.  Instead, it is included multiple times by gen8_private.h.
+ * directly.  Instead, it is included multiple times by anv_private.h.
  * 
  * In this header file, the usual genx() macro is available.
  */
 
+#ifndef ANV_PRIVATE_H
+#error This file is included by means other than anv_private.h
+#endif
+
 VkResult genX(init_device_state)(struct anv_device *device);
 
 void genX(cmd_buffer_emit_state_base_address)(struct anv_cmd_buffer *cmd_buffer);