RDMA/hns: Fix signed-unsigned mix with relational

driver inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I87LLN



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The ib_mtu_enum_to_int() and uverbs_attr_get_len() may returns a negative
value. In this case, mixed comparisons of signed and unsigned types will
throw wrong results.

This patch adds judgement for this situation.

Fixes: 30b70788 ("RDMA/hns: Support inline data in extented sge space for RC")
Signed-off-by: Chengchang Tang <tangchengchang@huawei.com>