libcamera: buffer: Drop forward declaration of BufferPool

There is no need to forward declare BufferPool, drop it.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

include/libcamera/buffer.h

@@ -13,7 +13,6 @@
 
 namespace libcamera {
 
-class BufferPool;
 class Request;
 class Stream;