LU-6142 libcfs: resolve debug.c checkpatch issues

LU-6142 libcfs: resolve debug.c checkpatch issues

Cleanup up libcfs debug.c to resolve various checkpatch issues.
This also brings us into alignment with the Linux Lustre client.

Change-Id: I011a11ce7f0d5189186f5f9d8e32954ec0ce1ff7
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/39118
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.super@gmail.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Oleg Drokin <green@whamcloud.com>