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

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

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

This patch also fixes few space/tab issues reported
by checkpatch

Test-Parameters: trivial
Signed-off-by: Arshad Hussain <arshad.super@gmail.com>
Change-Id: I6bdc084ca73163b88b2dd105b44b9a3cb611a999
Reviewed-on: https://review.whamcloud.com/36646
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Shaun Tancheff <stancheff@cray.com>
Reviewed-by: Petros Koutoupis <pkoutoupis@cray.com>
Reviewed-by: Neil Brown <neilb@suse.de>