LU-9859 libcfs: remove prng

LU-9859 libcfs: remove prng

The cfs prng is no longer used, so discard it.

Linux-commit: 508d5e0f4d45a815a0759c6aea69fef62359cf74

Test-Parameters: trivial

Change-Id: If780690dba196c8bc5935be223a952442f6a33ae
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-on: https://review.whamcloud.com/35351
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Shaun Tancheff <stancheff@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>