LU-12923 mdc: Use BUILD_BUG_ON() for mdc_request.c

LU-12923 mdc: Use BUILD_BUG_ON() for mdc_request.c

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

Test-Parameters: trivial
Signed-off-by: Arshad Hussain <arshad.super@gmail.com>
Change-Id: Ib04ddcb9d93c99cebdb175b39aceca0c25b12a10
Reviewed-on: https://review.whamcloud.com/36722
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Petros Koutoupis <pkoutoupis@cray.com>
Reviewed-by: Ben Evans <bevans@cray.com>
Reviewed-by: Shaun Tancheff <stancheff@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>