LU-9859 libcfs: move cfs_expr_list_print to nidstrings.c

LU-9859 libcfs: move cfs_expr_list_print to nidstrings.c

cfs_expr_list_print() is only called from nidstrings.c
so move it there and make it static.

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: Ie30aba19fd7935ba424c9212a81e7d0d91ad6f57
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/50834
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: Oleg Drokin <green@whamcloud.com>