amdgpu: add missing extern "C" headers

Signed-off-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Alex Xie <AlexBin.Xie@amd.com>

amdgpu/amdgpu.h

@@ -37,6 +37,10 @@
 #include <stdint.h>
 #include <stdbool.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 struct drm_amdgpu_info_hw_ip;
 
 /*--------------------------------------------------------------------------*/
@@ -1324,4 +1328,8 @@ int amdgpu_cs_destroy_semaphore(amdgpu_semaphore_handle sem);
 */
 const char *amdgpu_get_marketing_name(amdgpu_device_handle dev);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* #ifdef _AMDGPU_H_ */