IB/hns: Fix two bugs for rdma cm connecting

This patch mainly modify the value of HNS_ROCE_SL_SHIFT
and delete the lines for assigning for the field of
local_enable_e2e_credit in QP1C.

Signed-off-by: Lijun Ou <oulijun@huawei.com>
Reviewed-by: Wei Hu <xavier.huwei@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>