net: dsa: sja1105: fix buffer overflow in sja1105_setup_devlink_regions()

If an error occurs in dsa_devlink_region_create(), then 'priv->regions'
array will be accessed by negative index '-1'.

Found by Linux Verification Center (linuxtesting.org) with SVACE.
Signed-off-by: Rustam Subkhankulov <subkhankulov@ispras.ru>
Fixes: bf425b82 ("net: dsa: sja1105: expose static config as devlink region")
Link: https://lore.kernel.org/r/20220817003845.389644-1-subkhankulov@ispras.ruSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/sja1105/sja1105_devlink.c

@@ -93,7 +93,7 @@ static int sja1105_setup_devlink_regions(struct dsa_switch *ds)
 
 		region = dsa_devlink_region_create(ds, ops, 1, size);
 		if (IS_ERR(region)) {
-			while (i-- >= 0)
+			while (--i >= 0)
 				dsa_devlink_region_destroy(priv->regions[i]);
 			return PTR_ERR(region);
 		}