libcamera: Document documentation style and update the code accordingly

The documentation style for the Doxygen comment blocks is inconsistent
in the library. Document the expectations and update all existing
comment blocks to match.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Jacopo Mondi <jacopo@jmondi.org>

src/libcamera/request.cpp

@@ -90,7 +90,6 @@ int Request::setBuffers(const std::map<Stream *, Buffer *> &streamMap)
 /**
  * \brief Return the buffer associated with a stream
  * \param[in] stream The stream the buffer is associated to
- *
  * \return The buffer associated with the stream, or nullptr if the stream is
  * not part of this request
  */