drm/qxl: add extern C guard for the UAPI header

Cc: Gerd Hoffmann <[e-mail]>
Cc: Dave Airlie <[e-mail]>
Signed-off-by: Emil Velikov <[e-mail]>

include/uapi/drm/qxl_drm.h

···
 
 #include "drm.h"
 
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
 /* Please note that modifications to all structs defined here are
  * subject to backwards-compatibility constraints.
  *
···
 #define DRM_IOCTL_QXL_ALLOC_SURF \
 	DRM_IOWR(DRM_COMMAND_BASE + DRM_QXL_ALLOC_SURF,\
 		struct drm_qxl_alloc_surf)
+
+#if defined(__cplusplus)
+}
+#endif
 
 #endif