LU-13805 llite: Rename ldp_aio to sdio

LU-13805 llite: Rename ldp_aio to sdio

ldp_aio is a weird name for a 'sub dio' struct - rename it
to sdio.

Test-parameters: trivial
Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: Ie6f75e420e4bf4069af36c802b51063f02981613
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/50170
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Qian Yingjin <qian@ddn.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>