nvmet-rdma: fix kernel-doc warning for nvmet_rdma_device_removal

This fixes following kernel-doc warning:-

drivers/nvme/target/rdma.c:1722: warning: expecting prototype for nvme_rdma_device_removal(). Prototype was for nvmet_rdma_device_removal() instead

Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>