drm/xe/display: Add i915_gem.h compatibility header

Add i915_gem.h compatibility header and include it in i915_drv.h. Add
empty GEM_BUG_ON definition for fbc code.

Signed-off-by: Jouni Högander <[e-mail]>
Reviewed-by: Maarten Lankhorst <[e-mail]>
Signed-off-by: Rodrigo Vivi <[e-mail]>

drivers/gpu/drm/xe/compat-i915-headers/i915_drv.h

···
 #include "xe_bo.h"
 #include "xe_pm.h"
 #include "xe_step.h"
+#include "i915_gem.h"
 #include "i915_gem_stolen.h"
 #include "i915_gpu_error.h"
 #include "i915_reg_defs.h"

drivers/gpu/drm/xe/compat-i915-headers/i915_gem.h

···
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2023 Intel Corporation
+ */
+
+#ifndef __I915_GEM_H__
+#define __I915_GEM_H__
+#define GEM_BUG_ON
+#endif