EX-8270 ptlrpc: rename 'epp' to 'ppp'

EX-8270 ptlrpc: rename 'epp' to 'ppp'

Finish removing 'encryption' from page pool names except
for the module parameter, which is exposed in configuration
and so can't be changed.

Test-Parameters: trivial
Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: I1c14f6cf8cf1a19d89b5a7787aac1b67203866d3
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/52431
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>