Fix missing kfree in pvrdma_register_device() when failure from
ib_device_set_netdev().

Fixes: 4b38da75 ("RDMA/drivers: Convert easy drivers to use ib_device_set_netdev()")
Link: https://lore.kernel.org/r/20201111032202.17925-1-miaoqinglang@huawei.comReported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NQinglang Miao <miaoqinglang@huawei.com>
Signed-off-by: NJason Gunthorpe <jgg@nvidia.com>