libcamera: Move file_descriptor.h to base/

The FileDescriptor class is a generic helper that matches the criteria
for the base library. Move it there.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

include/libcamera/internal/ipc_pipe.h

@@ -9,10 +9,9 @@
 
 #include <vector>
 
+#include <libcamera/base/file_descriptor.h>
 #include <libcamera/base/signal.h>
 
-#include <libcamera/file_descriptor.h>
-
 #include "libcamera/internal/ipc_unixsocket.h"
 
 namespace libcamera {