ext4: remove cantfind_ext4 error handler

The 'cantfind_ext4' error handler is just a error msg print and then
goto failed_mount. This two level goto makes the code complex and not
easy to read. The only benefit is that is saves a little bit code.
However some branches can merge and some branches dot not even need it.
So do some refactor and remove it.

Signed-off-by: Jason Yan <yanaijie@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Link: https://lore.kernel.org/r/20220916141527.1012715-3-yanaijie@huawei.com


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