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/timer.cpp

@@ -44,7 +44,7 @@ Timer::Timer()
 
 /**
  * \brief Start or restart the timer with a timeout of \a msec
- * \param msec The timer duration in milliseconds
+ * \param[in] msec The timer duration in milliseconds
  *
  * If the timer is already running it will be stopped and restarted.
  */