scsi: RDMA/srp: Declare the SCSI host template const

Make it explicit that the SRP host template is not modified.

Acked-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20230322195515.1267197-7-bvanassche@acm.org


Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>