ext4: use ext4_group_desc_free() in ext4_put_super() to save some duplicated code

The only difference here is that ->s_group_desc and ->s_flex_groups share
the same rcu read lock here but it is not necessary. In other places they
do not share the lock at all.

Signed-off-by: Jason Yan <yanaijie@huawei.com>
Link: https://lore.kernel.org/r/20230323140517.1070239-4-yanaijie@huawei.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>