net: dsa: mv88e6xxx: Fix memleak in mv88e6xxx_region_atu_snapshot

When mv88e6xxx_fid_map return error, we lost free the table.

Fix it.

Fixes: bfb25542

 ("net: dsa: mv88e6xxx: Add devlink regions")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhangxiaoxu <zhangxiaoxu5@huawei.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20201109144416.1540867-1-zhangxiaoxu5@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>