RDMA/rtrs: server: Fix error handling in get_or_create_srv

RDMA/rtrs: server: Fix error handling in get_or_create_srv

After device_initialize() is called, use put_device() to release the
device according to kernel device management rules. While direct
kfree() work in this case, using put_device() is more correct.

Found by code review.

Fixes: 9cb837480424 ("RDMA/rtrs: server: main functionality")
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
Link: https://patch.msgid.link/20251110005158.13394-1-make24@iscas.ac.cn
Acked-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>