ext4: get rid of ppath in ext4_ext_create_new_leaf()

ext4: get rid of ppath in ext4_ext_create_new_leaf()

The use of path and ppath is now very confusing, so to make the code more
readable, pass path between functions uniformly, and get rid of ppath.

To get rid of the ppath in ext4_ext_create_new_leaf(), the following is
done here:

 * Free the extents path when an error is encountered.
 * Its caller needs to update ppath if it uses ppath.

No functional changes.

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/20240822023545.1994557-14-libaokun@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>