elevator: make the rqhash helpers exported

Signed-off-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>

path: root/Sponsors

netsniff-ng is partly sponsored by:
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Red Hat
 * W: http://www.redhat.com/

Deutsche Flugsicherung GmbH
 * W: https://secais.dfs.de/

ETH Zurich:
 * W: http://csg.ethz.ch/

Max Planck Institute for Human Cognitive and Brain Sciences
 * W: http://www.cbs.mpg.de/