i40iw: Fix error handling in i40iw_manage_arp_cache()

The i40iw_arp_table() function can return -EOVERFLOW if
i40iw_alloc_resource() fails so we can't just test for "== -1".

Fixes: 4e9042e6 ("i40iw: add hw and utils files")
Link: https://lore.kernel.org/r/20200422092211.GA195357@mwandaSigned-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/i40iw/i40iw_hw.c

@@ -534,7 +534,7 @@ void i40iw_manage_arp_cache(struct i40iw_device *iwdev,
 	int arp_index;
 
 	arp_index = i40iw_arp_table(iwdev, ip_addr, ipv4, mac_addr, action);
-	if (arp_index == -1)
+	if (arp_index < 0)
 		return;
 	cqp_request = i40iw_get_cqp_request(&iwdev->cqp, false);
 	if (!cqp_request)