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

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>

include/uapi/drm/savage_drm.h

@@ -28,6 +28,10 @@
 
 #include "drm.h"
 
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
 #ifndef __SAVAGE_SAREA_DEFINES__
 #define __SAVAGE_SAREA_DEFINES__
 
@@ -209,4 +213,8 @@ union drm_savage_cmd_header {
 	} clear1;		/* SAVAGE_CMD_CLEAR data */
 };
 
+#if defined(__cplusplus)
+}
+#endif
+
 #endif