libcamera: camera: Don't check buffer count before freeing buffers

There's no need to check if buffers have been allocated before freeing
them as the BufferPool::destroyBuffers() method is a no-op when no
buffers have been allocated. Document this fact explicitly, and remove
the buffer count check.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

src/libcamera/buffer.cpp

@@ -311,6 +311,9 @@ void BufferPool::createBuffers(unsigned int count)
 
 /**
  * \brief Release all buffers from pool
+ *
+ * If no buffers have been created or if buffers have already been released no
+ * operation is performed.
  */
 void BufferPool::destroyBuffers()
 {