LU-12923 lov: Use BUILD_BUG_ON() for lov_pack.c

LU-12923 lov: Use BUILD_BUG_ON() for lov_pack.c

This patch replaces all CLASSERT() with kernel defined
BUILD_BUG_ON() for file lustre/lov/lov_pack.c

Test-Parameters: trivial
Signed-off-by: Arshad Hussain <arshad.super@gmail.com>
Change-Id: Ic59b482e73cf2556247153ecde658ded57b603f9
Reviewed-on: https://review.whamcloud.com/36718
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Petros Koutoupis <pkoutoupis@cray.com>
Reviewed-by: Ben Evans <bevans@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>