libcamera: request: Clarify ReuseBuffers flag usage with fences

Explicitly clarify the usage of Request::ReuseBuffers flag in context
of buffer fences. Fences are user-supplied and are not re-cycled as
part of Request::reuse(), hence document this behaviour explicitly.

Signed-off-by: Umang Jain <uajain@igalia.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>

src/libcamera/request.cpp

@@ -327,6 +327,9 @@ void Request::Private::timeout()
  * Don't reuse buffers
  * \var Request::ReuseBuffers
  * Reuse the buffers that were previously added by addBuffer()
+ *
+ * \note Fences associated with the buffers are not reused.
+ *  This flag should not be used if fences are used.
  */
 
 /**