LU-17831 llite: remove PageLocked assert

LU-17831 llite: remove PageLocked assert

This pagelocked assert touches the spinlock and costs us
about 5% of our performance when dropping pages.

Signed-off-by: Patrick Farrell <patrick.farrell@oracle.com>
Change-Id: Ie67f45fc0131d3fa94b70e3734ade2139c481301
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/55053
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>