stmmac, xsk: Diversify return values from xsk_wakeup call paths

Currently, when debugging AF_XDP workloads, one can correlate the -ENXIO
return code as the case that XSK is not in the bound state. Returning
same code from ndo_xsk_wakeup can be misleading and simply makes it
harder to follow what is going on.

Change ENXIOs in stmmac's ndo_xsk_wakeup() implementation to EINVALs, so
that when probing it is clear that something is wrong on the driver
side, not the xsk_{recv,send}msg.

There is a -ENETDOWN that can happen from both kernel/driver sides
though, but I don't have a correct replacement for this on one of the
sides, so let's keep it that way.
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220413153015.453864-13-maciej.fijalkowski@intel.com

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -6565,7 +6565,7 @@ int stmmac_xsk_wakeup(struct net_device *dev, u32 queue, u32 flags)
 		return -ENETDOWN;
 
 	if (!stmmac_xdp_is_enabled(priv))
-		return -ENXIO;
+		return -EINVAL;
 
 	if (queue >= priv->plat->rx_queues_to_use ||
 	    queue >= priv->plat->tx_queues_to_use)
@@ -6576,7 +6576,7 @@ int stmmac_xsk_wakeup(struct net_device *dev, u32 queue, u32 flags)
 	ch = &priv->channel[queue];
 
 	if (!rx_q->xsk_pool && !tx_q->xsk_pool)
-		return -ENXIO;
+		return -EINVAL;
 
 	if (!napi_if_scheduled_mark_missed(&ch->rxtx_napi)) {
 		/* EQoS does not have per-DMA channel SW interrupt,