ext4: Free resources in some error path in ext4_fill_super

Some of the error path in ext4_fill_super don't release the
resouces properly. So this patch just try to release them
in the right way.

Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>