nfp: flower: add check for flower VF netdevs for get/set_eeprom

Move the nfp_net_get_port_mac_by_hwinfo() check to ahead in the
get/set_eeprom() functions to in order to check for a VF netdev, which
this function does not support.

It is debatable if this is a fix or an enhancement, and we have chosen
to go for the latter. It does address a problem introduced by
commit 74b4f173 ("nfp: flower: change get/set_eeprom logic and enable for flower reps").
However, the ethtool->len == 0 check avoids the problem manifesting as a
run-time bug (NULL pointer dereference of app).
Signed-off-by: James Hershaw <james.hershaw@corigine.com>
Reviewed-by: Louis Peens <louis.peens@corigine.com>
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Link: https://lore.kernel.org/r/20230206154836.2803995-1-simon.horman@corigine.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/netronome/nfp/nfp_net_ethtool.c

@@ -1908,12 +1908,12 @@ nfp_net_get_eeprom(struct net_device *netdev,
 	struct nfp_app *app = nfp_app_from_netdev(netdev);
 	u8 buf[NFP_EEPROM_LEN] = {};
 
-	if (eeprom->len == 0)
-		return -EINVAL;
-
 	if (nfp_net_get_port_mac_by_hwinfo(netdev, buf))
 		return -EOPNOTSUPP;
 
+	if (eeprom->len == 0)
+		return -EINVAL;
+
 	eeprom->magic = app->pdev->vendor | (app->pdev->device << 16);
 	memcpy(bytes, buf + eeprom->offset, eeprom->len);
 
@@ -1927,15 +1927,15 @@ nfp_net_set_eeprom(struct net_device *netdev,
 	struct nfp_app *app = nfp_app_from_netdev(netdev);
 	u8 buf[NFP_EEPROM_LEN] = {};
 
+	if (nfp_net_get_port_mac_by_hwinfo(netdev, buf))
+		return -EOPNOTSUPP;
+
 	if (eeprom->len == 0)
 		return -EINVAL;
 
 	if (eeprom->magic != (app->pdev->vendor | app->pdev->device << 16))
 		return -EINVAL;
 
-	if (nfp_net_get_port_mac_by_hwinfo(netdev, buf))
-		return -EOPNOTSUPP;
-
 	memcpy(buf + eeprom->offset, bytes, eeprom->len);
 	if (nfp_net_set_port_mac_by_hwinfo(netdev, buf))
 		return -EOPNOTSUPP;