LU-16621 enc: file names encryption when using secure boot

LU-16621 enc: file names encryption when using secure boot

Secure boot activates lockdown mode in the Linux kernel.
And debugfs is restricted when the kernel is locked down.
This patch moves file names encryption from debugfs to sysfs.

Lustre-change: https://review.whamcloud.com/50219
Lustre-commit: 716675fff642655c4d4715654b0b4880b96139b6

Test-Parameters: trivial testlist=sanity-sec
Signed-off-by: Alex Deiter <alex.deiter@gmail.com>
Change-Id: I434714941ffac2a4694cabd33f613aef70933678
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/50578
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>