ext4: get rid of ppath in ext4_ext_convert_to_initialized()

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_convert_to_initialized(), the following
is done here:

 * Free the extents path when an error is encountered.
 * Its caller needs to update ppath if it uses ppath.
 * The 'allocated' is changed from passing a value to passing an address.

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/20240822023545.1994557-21-libaokun@huaweicloud.com


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