LU-4974 lod: Change pool_desc to "[lod|lov]_pool_desc"

LU-4974 lod: Change pool_desc to "[lod|lov]_pool_desc"

This patch changes 'struct pool_desc' under lov and lod
to 'lov_pool_struct' and 'lod_pool_struct' respectively.
This is the first step to check if there is anything
common and can be unify. Although both layer uses
'struct pool_desc' to define the pool_desc struct
respectively. 'struct pool_desc' under lod has changed
and grown. Therefore to remove ambiguity, prefix lod/lov
is added to pool_desc struct for respective layer.

This patch also adds function description wherever
applicable

This patch also changes space/tabs reported by
checkpatch

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: I3fee3f2e9c321145779d9177a8e4582d123f1e8d
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/11114
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>