RDMA/hns: Fix uninitialized variable

A random value will be returned if the condition below is not met, so it
needs to be initialized.

Fixes: 9ea9a53e ("RDMA/hns: Add mapped page count checking for MTR")
Link: https://lore.kernel.org/r/1624011020-16992-3-git-send-email-liweihang@huawei.com


Signed-off-by: Yixing Liu <liuyixing1@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>