RDMA/hns: Use a constant instead of sizeof operation

driver inclusion
category: cleanup
bugzilla: https://gitee.com/openeuler/kernel/issues/I5USIG



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The sge size is known to be constant, so it's unnecessary to use sizeof to
calculate.

Fixes: 30b70788 ("RDMA/hns: Support inline data in extented sge space for RC")

Signed-off-by: Luoyouming <luoyouming@huawei.com>
Reviewed-by: Yangyang Li <liyangyang20@huawei.com>
Reviewed-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>