LU-8066 lov: move stripesize to sysfs

LU-8066 lov: move stripesize to sysfs

One lonely simple proc file exist for lov. Move stripesize to
sysfs.

Lustre-change: https://review.whamcloud.com/43212
Lustre-commit: 28bac98fcb44aabb08258121fcfd39eb46cff0d7

Change-Id: I4db660f0e7af4d69c697f8c73547a245108adb9b
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/49837
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>