RDMA/hns: Fix usage of bitmap allocation functions return values

hns bitmap allocation functions return 0 on success and -1 on failure.
Callers of these functions wrongly used their return value as an errno,
fix that by making a proper conversion.

Fixes: a598c6f4 ("IB/hns: Simplify function of pd alloc and qp alloc")
Signed-off-by: Gal Pressman <pressmangal@gmail.com>
Acked-by: Lijun Ou <oulijun@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>