nvme-fcloop: no need to return from void function

Remove return at the end of void function.

Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>