RDMA/hns: Remove redundant member doorbell_qpn of struct hns_roce_qp

mainline inclusion
from mainline-v6.1-rc1
commit bfb3bde9
category: cleanup
bugzilla: https://gitee.com/openeuler/kernel/issues/I7UVH7
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=bfb3bde95479e7072839564ec90dbf5d00bfb9b1

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The value of doorbell_qpn is always equal to qpn on current hardware
versions. So remove it.

Link: https://lore.kernel.org/r/20220829105021.1427804-5-liangwenpeng@huawei.com


Signed-off-by: Wenpeng Liang <liangwenpeng@huawei.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Juan Zhou <zhoujuan51@h-partners.com>