jbd2: use bh_in instead of jh2bh(jh_in) to simplify code

We save jh2bh(jh_in) to bh_in, so use bh_in directly instead of
jh2bh(jh_in) to simplify the code.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20240514112438.1269037-7-shikemeng@huaweicloud.com


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