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

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>

include/uapi/drm/amdgpu_drm.h

@@ -34,6 +34,10 @@
 
 #include "drm.h"
 
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
 #define DRM_AMDGPU_GEM_CREATE		0x00
 #define DRM_AMDGPU_GEM_MMAP		0x01
 #define DRM_AMDGPU_CTX			0x02
@@ -642,4 +646,8 @@ struct drm_amdgpu_info_hw_ip {
 #define AMDGPU_FAMILY_VI			130 /* Iceland, Tonga */
 #define AMDGPU_FAMILY_CZ			135 /* Carrizo, Stoney */
 
+#if defined(__cplusplus)
+}
+#endif
+
 #endif