RDMA/srp: Fix error handling in srp_add_port

RDMA/srp: Fix error handling in srp_add_port

As comment of device_add() says, if device_add() succeeds, you should
call device_del() when you want to get rid of it. If device_add() has
not succeeded, use only put_device() to drop the reference count.

Add a put_device() call before returning from the function to decrement
reference count for cleanup.

Found by code review.

Fixes: c8e4c2397655 ("RDMA/srp: Rework the srp_add_port() error path")
Signed-off-by: Ma Ke <make_ruc2021@163.com>
Link: https://patch.msgid.link/20241217075538.2909996-1-make_ruc2021@163.com
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Leon Romanovsky <leon@kernel.org>