nvme-rdma: fix the return value of nvme_rdma_reinit_request()

PTR_ERR should be applied before its argument is reassigned, otherwise the
return value will be set to 0, not error code.
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Reviewed-by: Jay Freyensee <james_p_freyensee@linux.intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/nvme/host/rdma.c

@@ -299,8 +299,8 @@ static int nvme_rdma_reinit_request(void *data, struct request *rq)
 	req->mr = ib_alloc_mr(dev->pd, IB_MR_TYPE_MEM_REG,
 			ctrl->max_fr_pages);
 	if (IS_ERR(req->mr)) {
-		req->mr = NULL;
 		ret = PTR_ERR(req->mr);
+		req->mr = NULL;
 	}
 
 	req->need_inval = false;