RDMA/hns: Fix a missing check of atomic wr length

driver inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7A2SA



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The only supported length of atomic wr in kernel space is 8. The
driver needs to check the length before post send.

Fixes: 00a59d30 ("RDMA/hns: Optimize wqe buffer filling process for post send")
Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
(cherry picked from commit 555adba6)