libcamera: v4l2_videodevice: Use FileDescriptor "fd move" constructor

Use the newly added "fd move" constructor of the FileDescriptor class to
avoid dup() + close().

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

src/libcamera/v4l2_videodevice.cpp

@@ -1276,14 +1276,7 @@ FileDescriptor V4L2VideoDevice::exportDmabufFd(unsigned int index,
 		return FileDescriptor();
 	}
 
-	FileDescriptor fd(expbuf.fd);
-	/*
-	 * FileDescriptor takes a duplicate of fd, so we must close the
-	 * original here, otherwise it will be left dangling.
-	 */
-	::close(expbuf.fd);
-
-	return fd;
+	return FileDescriptor(std::move(expbuf.fd));
 }
 
 /**