ext4: refactor ext4_ext_rm_idx() to index 'path'

ext4: refactor ext4_ext_rm_idx() to index 'path'

As suggested by Honza in Link，modify ext4_ext_rm_idx() to leave 'path'
alone and just index it like ext4_ext_correct_indexes() does it. This
facilitates adding error handling later. No functional changes.

Suggested-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/all/20230216130305.nrbtd42tppxhbynn@quack3/
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/20240822023545.1994557-2-libaokun@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>