ext4: add new ext4_ext_path_brelse() helper

Add ext4_ext_path_brelse() helper function to reduce duplicate code
and ensure that path->p_bh is set to NULL after it is released.

Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Tested-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://patch.msgid.link/20240822023545.1994557-10-libaokun@huaweicloud.com


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