nexthop: Fix off-by-one error in error path

A reference was not taken for the current nexthop entry, so do not try
to put it in the error path.

Fixes: 430a049190 ("nexthop: Add support for nexthop groups")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/nexthop.c

@@ -1459,7 +1459,7 @@ static struct nexthop *nexthop_create_group(struct net *net,
 	return nh;
 
 out_no_nh:
-	for (; i >= 0; --i)
+	for (i--; i >= 0; --i)
 		nexthop_put(nhg->nh_entries[i].nh);
 
 	kfree(nhg->spare);