libcamera: Fix spellings and grammar

Fix a number of spelling errors and word duplications throughout the comments
within libcamera.

These were picked up with spellintian.

Also one capitalisation of the first word of a \return statement picked
up by checkstyle.py while creating this patch.

Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/libcamera/stream.cpp

@@ -649,7 +649,7 @@ void Stream::destroyBuffers()
  * \var Stream::bufferPool_
  * \brief The pool of buffers associated with the stream
  *
- * The stream buffer pool is populated by the Camera class after a succesfull
+ * The stream buffer pool is populated by the Camera class after a successful
  * stream configuration.
  */