drm/i915/display: add I915 conditional build to intel_overlay.h

Add stubs for !I915.
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/45a127d37816ac97dfe493beeed060e323047014.1694514689.git.jani.nikula@intel.com

drivers/gpu/drm/i915/display/intel_overlay.h

@@ -13,6 +13,7 @@ struct drm_i915_private;
 struct intel_overlay;
 struct intel_overlay_error_state;
 
+#ifdef I915
 void intel_overlay_setup(struct drm_i915_private *dev_priv);
 void intel_overlay_cleanup(struct drm_i915_private *dev_priv);
 int intel_overlay_switch_off(struct intel_overlay *overlay);
@@ -25,5 +26,39 @@ struct intel_overlay_error_state *
 intel_overlay_capture_error_state(struct drm_i915_private *dev_priv);
 void intel_overlay_print_error_state(struct drm_i915_error_state_buf *e,
 				     struct intel_overlay_error_state *error);
+#else
+static inline void intel_overlay_setup(struct drm_i915_private *dev_priv)
+{
+}
+static inline void intel_overlay_cleanup(struct drm_i915_private *dev_priv)
+{
+}
+static inline int intel_overlay_switch_off(struct intel_overlay *overlay)
+{
+	return 0;
+}
+static inline int intel_overlay_put_image_ioctl(struct drm_device *dev, void *data,
+				  struct drm_file *file_priv)
+{
+	return 0;
+}
+static inline int intel_overlay_attrs_ioctl(struct drm_device *dev, void *data,
+					    struct drm_file *file_priv)
+{
+	return 0;
+}
+static inline void intel_overlay_reset(struct drm_i915_private *dev_priv)
+{
+}
+static inline struct intel_overlay_error_state *
+intel_overlay_capture_error_state(struct drm_i915_private *dev_priv)
+{
+	return NULL;
+}
+static inline void intel_overlay_print_error_state(struct drm_i915_error_state_buf *e,
+						   struct intel_overlay_error_state *error)
+{
+}
+#endif
 
 #endif /* __INTEL_OVERLAY_H__ */