sysfs: reposition sysfs_dirent->s_mode.

Move s_mode downward such that it's side-by-side with s_iattr which is
used for the same thing.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>