RDMA/hns: Optimize hns_roce_alloc_vf_resource()

The capbilities of hardware should be got at first and then used in
hns_roce_alloc_vf_resource(). Also removes an unnecessary if ... else
condition in it.

Link: https://lore.kernel.org/r/1584674622-52773-5-git-send-email-liweihang@huawei.com


Signed-off-by: Lijun Ou <oulijun@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>