RDMA/srpt: Duplicate port name members

Prepare for decoupling the lifetimes of struct srpt_port and struct
srpt_port_id by duplicating the port name into struct srpt_port.

Link: https://lore.kernel.org/r/20220727193415.1583860-2-bvanassche@acm.org


Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>