RDMA/hns: Fix unmatched condition in error path of alloc_user_qp_db()

RDMA/hns: Fix unmatched condition in error path of alloc_user_qp_db()

Currently the condition of unmapping sdb in error path is not exactly
the same as the condition of mapping in alloc_user_qp_db(). This may
cause a problem of unmapping an unmapped db in some case, such as
when the QP is XRC TGT. Unified the two conditions.

Fixes: 90ae0b57e4a5 ("RDMA/hns: Combine enable flags of qp")
Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
Link: https://patch.msgid.link/20250311084857.3803665-4-huangjunxian6@hisilicon.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>